The State of Texas filed this suit to obtain a permanent injunction restraining Shoppers World, Inc., from violating Article 286a, Vernon’s Ann.Penal Code, by selling or offering for sale certain merchandise on the consecutive days of Saturday and Sunday. Shoppers World defended on the ground that the sales and offers for sale strictly complied with the emergency purchase exemption contained in Section 4a of that article. The trial court granted the injunction, but its judgment was reversed and the injunction was dissolved by the Court of Civil Appeals, 373 S.W.2d 374.
We affirm the judgment of the Court of Civil Appeals.
The applicable sections of Art. 286a, Vernon’s Ann.Penal Code provide:
“Section 1. Any person, on both the two (2) consecutive days of Saturday and Sunday, who sells or offers for sale or shall compel, force or oblige his employees to sell any clothing; clothing accessories; wearing apparel; footwear; headwear; home, business, office or outdoor furniture; kitchenware; kitchen utensils; china; home appliances; stoves; refrigerators; air conditioners; electric fans; radios; television sets; washing machines; driers; cameras; hardware; tools, excluding non-power driven hand tools; jewelry; precious or semi-precious stones; silverware; watches; clocks; luggage; motor vehicles; musical instruments ; recordings; toys, excluding items customarily sold as novelties and souvenirs; mattresses; bed coverings; household linens; floor coverings; lamps; draperies; blinds; curtains; mirrors; lawn mowers or cloth piece goods shall be guilty of a misdemeanor. Each separate sale shall constitute a separate offense.
«5{C * *
“Sec. 4a. When a purchaser will certify in writing that a purchase of an item of personal property is needed as an emergency for the welfare, health or safety of human or animal life and such purchase is an emergency purchase to protect the health, welfare or safety of human or animal life, then this Act shall not apply; provided such certification signed by the purchaser is retained by the merchant for proper inspection for a period of one (1) year.”
An agreed statement of facts was submitted to the trial court in accordance with Rule 263, Texas Rules of Civil Procedure. Only those facts material to our decision will be noted. Respondent’s store, located in Corpus Christi, is open for business on both Saturday and Sunday. The store sells and offers for sale one or more of the *109items enumerated in Art. 286a on the consecutive days of Saturday and Sunday, but on Sunday these items are sold and offered for sale only to those purchasers who will sign a form labeled “Certificate of Necessity.” The certificate is prepared in the language of Sec. 4a:
“I hereby certify that the following item(s) of personal property are needed by me as an emergency for the welfare (-) of human (-) . life;
[here follows a space for listing the items purchased] and that the purchase of each such item is an emergency purchase to protect the welfare (-) of human (-) life, and I have so advised Shoppers World, from whom I have purchased such item(s).
Signature”
At the check-out stand the purchaser lists the items on the certificate, and the cashier employee of the respondent reads this statement to the purchaser:
“If this purchase is an emergency purchase for the health, welfare or safety of human or animal life, please sign this certificate.”
If the purchaser signs the certificate without hesitancy, the sale is made without further explanation or inquiry. If the purchaser refuses to sign, the sale is not made. If the customer is hesitant about signing, the store manager explains that the store is prohibited by law from selling particular items on the consecutive days of Saturday and Sunday unless the purchaser certifies in writing that the item is needed by the purchaser as an emergency for the welfare, health or safety of human or animal life and the purchase is an emergency purchase to protect the health, welfare or safety of human or animal life. The store manager then questions the purchaser about the existence and nature of the emergency. If after the explanation and inquiry the purchaser remains uncertain about signing the certificate, the item or items are not sold but are returned to the store shelves. These certificates are retained at the respondent’s store for inspection.
No evidence other than the agreed statement of facts was heard or introduced in the trial court, yet the trial judge found additional facts which, presumably, entered into the judgment. In brief, he found that the certificates of necessity were used as a device for evading the prohibitions of Art. 286a, and that respondent acted in bad faith in having the purchasers sign the certificates. Based upon such findings, the trial court entered judgment permanently enjoining Shoppers World from selling or offering for sale the items enumerated in Art. 286a on the consecutive days of Saturday and Sunday, but the injunction further provided:
“This injunction does not prevent a sale of any of such enumerated items on the second of two consecutive days of Saturday and Sunday when the purchaser initiates the sale by offering to purchase without a prior offer on the part of the Defendant, Shoppers World, Inc., to sell and the purchaser will certify in writing that a purchase of such items of personal property is needed as an emergency for the welfare, health or safety of human or animal life, which said certification signed by the purchaser is retained by Defendant Shoppers World, Inc., for proper inspection for a period of one year, and such purchase is, in fact, an emergency purchase to protect the health, welfare or safety of human or animal life believed by Defendant Shoppers World, Inc., after inquiry, on reasonable grounds, in the exercise of good faith, to be such emergency purchase.” 1
The Court of Civil Appeals dissolved the injunction on the ground that by includ*110ing the emphasized portion in the judgment the trial court had added more onerous conditions to the exemption of Sec. 4a than those imposed by the Legislature.
The disposition of this case turns on the proper interpretation of the provision in Sec. ,4a which we repeat:
“When a purchaser will certify in writing that a purchase of an item of per- ' sonal property is needed as an emergency for the welfare, health or safety of human or animal life and such purchase is an emergency purchase to protect the' health, welfare or safety of ■ human or animal life, then this Act shall not apply; * * *.”
In Crouch v. Craik, Tex., 369 S.W.2d 311, 315, we stated: “The power and authority to interpret Articles 286, 286a and 287 [Vernon’s Penal Code] rests solely, with the courts of this state exercising criminal jurisdiction.” We must confess that the statement is much too broad. It is to be related to the context in which we were writing. The. statement was intended to explain our adherence to the rule that courts of equity will take jurisdiction to enjoin enforcement of penal laws only in exceptional situations, thus leaving those laws to be interpreted through the criminal trial process whenever possible. The procedure by which this case reaches us does not permit us to relegate the parties to the criminal trial process for interpretation of Art. 286a. Sec. 4 of the Article declares a business operating contrary to its provisions to be a public nuisance, and provides that “any person may apply to any court of competent jurisdiction for and may obtain an injunction restraining such violation of this Act.” That legislative direction requires the civil courts to interpret Art. 286a.2
The position of the State is that this provision requires that two conditions exist before the sale of 'an item listed in Sec. 1 will be exempted from the general prohibition of Art. 286a. First, the purchaser must certify in writing that the item is needed as an emergency for the welfare, health or safety of human or animal life. Second, the purchase must in fact be an emergency purchase to protect the health, welfare or safety of human or animal life. The basis of this argument is that by using the conjunction “and” between the two clauses of the provision the Legislature intended to create not only the certification requirement but also the requirement that the emergency exist in fact.
The respondent contends that the provision in clear and unambiguous terms imposes one requirement only — that the purchaser certify in writing (1) that the item is needed as an emergency, and (2) that the purchase is an emergency purchase. The position of respondent thus is that once the purchaser has certified that both conditions exist, the seller is free to complete the sale without regard to the existence of an actual emergency. The premise of this argument is that both clauses of the provision follow the words “certify in writing that,” and nothing indicates that the clauses should be considered to be making separate, distinct requirements. Alternatively, the respondent argues that if the clause is regarded as ambiguous, the State’s interpretation cannot be accepted because that interpretation would render the section unconstitutional.
We hold that the quoted provision is ambiguous and that it must be given the interpretation placed on it by respondent.
The guiding rule of statutory interpretation is to ascertain legislative intent. 53 Tex.Jur.2d 180, Statutes, § 125. When the intent is clear it will be given effect by the courts even to the extent of adding words to the language used by the *111Legislature. See Sweeny Hospital District v. Carr, Tex.Sup., 378 S.W.2d 40. Sometimes, however, legislative intent is elusive and unclear; and in such instances the courts must resort to rules of construction to give meaning to legislative enactments. That is the situation here.
If we could say that the interpretation placed on the quoted language of Sec. 4a by either of the parties was the only reasonable interpretation, we would regard our judicial obligation as at an end and would give the language that meaning. By interpolating the word “that” between the words “and” and “such purchase” in the second clause, the provision could be made to say clearly what respondent contends it now says. By interpolating the word “when” between the words “and” and “such purchase” the provision could he made to say clearly what petitioner contends it now says. Moreover, either revision would make the provision meaningful. Considered either as standing alone or in context with the remainder of the statute, or in pari ma-teria with Articles 286 and 287, we find no clue to legislative intent in the enactment of Sec. 4a which authorizes us to say that the one or the other revision is the only reasonable one. Neither do we find a clue to legislative intent in the legislative history of the enactment.
The statute had its origin in Senate Bill No. 35, passed by the First Called Session of the 57th Legislature. See Acts 57th Leg., 1st C.S., ch. 15, p. 38. Sec. 4a was not in the bill when it was introduced in the Senate; it w.as incorporated in the bill by amendment on third reading in the House of Representatives, and the amendment was adopted by unanimous consent. The language and punctuation of Sec. 4a is exactly as it appeared in the amendment. See House Journal, First' Called Session, page 843. Being thus unable to resolve the ambiguity in the section from the only sources available, we turn to rules of construction to resolve it. The controlling rule of construction here is that which requires that a statute not be giveii the one of 'two reasonable interpretations which will render it unconstitutional and void. See McKinney v. Blankenship, 54 Tex. 632, 282 S.W.2d 691, 697 ; 53 Tex.Jur.2d 225, Statutes, § 158.
If Sec. 4a is interpreted as respondent interprets it, the obligations imposed on the seller of items of personal property are clear and definite and the section is constitutional and valid. Under that interpretation, the right to sell or to offer to sell without incurring penal sanctions is conditioned alone and altogether on certification by buyers that items are needed as an emergency for the welfare, health or safety of human or animal life and that the purchase is in fact an emergency purchase to protect the health, welfare or safety of human or animal life. The right to sell or the duty not to sell are thus made to rest on a subjective determination by the purchaser of the emergency nature of the purchase and that it is to protect the welfare, health or safety of human or animal life. If the certificate is made, a sale may be made without fear of criminal punishment. If the certificate is not made, a sale may not be made without risk of criminal punishment.
The situation is quite different if Sec. 4a is interpreted as petitioner interprets it. Under that interpretation the seller must, with respect to every sale, make an objective determination as to whether the purchase is an emergency purchase and whether the items are needed to protect the health, welfare or safety of human or animal life. A sale can never be made without risk of incurring criminal penalties since the statute provides no guides or criteria for making the determination.
It is well settled that a penal statute may be so vague and indefinite that it violates the right guaranteed to an accused by Sec. 10, Art. 1, Texas Constitution, Vernon’s Ann.St., to “demand the nature and cause of the accusation against him.” Griffin v. State, 86 Cr.Rep. 498, 218 S.W. 494; *112Ex parte Slaughter, 92 Cr.Rep. 212, 243 S.W. 478, 26 A.L.R. 891. And even if we should accept Bradford v. State, 78 Cr.Rep. 285, 180 S.W. 702, and Baltimore & O. Ry. Co. v. Interstate Commerce Commission, 221 U.S. 612, 31 S.Ct. 621, 55 L.Ed. 878, as authority for saying that Sec. 4a is not void because of the indefinite character of the phrase “emergency purchase,” we must nevertheless hold the section void for indefiniteness of the phrase “to protect the * * * welfare * * * of human or animal life.”
How can a seller determine whether a purchase is an emergency purchase for the “welfare” of human or animal life? The word “welfare” has a variety of meanings, as respondent points out. Webster’s Third New International Dictionary defines “welfare” as “the state of faring or doing well: thriving or successful progress in life: a state characterized esp. by good fortune, happiness, well-being, or prosperity. * * one’s condition in regard to health, happiness, or prosperity.” It would seem obvious on the face of it that whether any particular purchase is an emergency purchase to protect the happiness or well-being of human life can be determined only subjectively by the purchaser; and that if the section be construed as imposing a duty on the seller to make an objective determination of the matter, he will be subjected to criminal penalties for failing to discharge an impossible obligation. Cases such as Gann v. Keith, 151 Tex. 626, 253 S.W.2d 413, which uphold the validity of statutes as prescribing rules of civil conduct though they may be too indefinite to predicate criminal proscriptions, are not applicable here. Art. 286a is strictly a penal statute, not a statute prescribing a rule of civil conduct. And even though this is a civil proceeding, penal sanctions would be imposed if respondent should violate the injunction and thus be in contempt.
Our holding of indefiniteness is a narrow one. It has been made narrow deliberately. We are not to be understood, however, as holding or inferring that we would uphold the validity of Sec. 4a if it required only that a seller make an objective determination as to whether a purchase is an emergency purchase. The reasoning in the decisions of the Supreme Court of Kansas in State of Kansas v. Hill, 189 Kan. 403, 369 P.2d 365, 91 A.L.R.2d 750, and the Supreme Court of Missouri in Harvey v. Priest, Mo., 366 S.W.2d 324, would be strongly persuasive against validity. In those cases it was held that Sunday closing laws which excepted sales of articles “of immediate necessity” were invalid for indefiniteness.
It is difficult to conceive of any set of circumstances under which a purchase of most of the articles listed in Section 1 of Art. 286a could be an “emergency purchase” as one would normally interpret that phrase; but by the provisions of Sec. 4a the Legislature has expressly said that a purchase of any of them may be, and it is not in our province to decree otherwise.
In order to uphold the constitutionality of Sec. 4a, we construe the section as requiring as a condition of the right to sell the listed articles on both Saturday and Sunday only a certificate of the purchaser that an item is needed as an emergency for the welfare, health or safety of human or animal life and that the purchase is in fact an emergency purchase to protect the health, welfare or safety of human or animal life. The certificate required by respondent is in strict compliance with the section. The duty is not imposed on respondent to determine whether the certificate is signed in good faith. The agreed facts do not show that respondent has been selling the listed items on both Saturday and Sunday without obtaining the certificate; and there is, therefore, no basis for the injunction granted by the trial court.
The judgment of the Court of Civil Appeals reversing the judgment of the trial court and dissolving the injunction is affirmed.
. Emphasis supplied throughout unless otherwise indicated.
. The Court of Criminal Appeals has held in Ex parte Wilson, 374 S.W.2d 229, that Sec. 5a does not render Art. 2SGn so indefinite as to invalidate it, but that court has not decided the question presented in this casé.