By the Court,
Whiton, C. J.The principal matters relied upon by the plaintiffs in error to reverse the judgment, relate to the construction which was given at the trial to the contract for the delivery of the wheat, and to the ruling of the court by which the testimony offered to impeach the witness Herring, was excluded from the jury.
The counsel for the plaintiffs in error contend that the performance of the agreement on their part to deliver the wheat, was dependent on the performance of the agreement on the part *129of tbe defendants in error to furnish the bags in which to haul it. The court below instructed the jury in effect, that these agreements of the parties were independent, and that the plaintiffs below might recover although they had not kept ther own agreement to furnish the bags. Questions of this kind most commonly arise in relation to covenants, but the same rule of construction must in this respect, we suppose, be applied to the construction of instruments under seal and to agreements like the one which is the foundation of this suit.
Generally, where the thing which the defendant undertakes to perform is in consideration of something to be done by the plaintiff, the performance on the part of the latter is a condition precedent to the obligation of the defendant. The plaintiff must, therefore, in such cases, aver in his declaration, and prove by ■testimony, that he has performed on his part, because the obligation of the defendant is dependent on the plaintiff’s performance.
Although this principle is quite familiar, it is sometimes not easy to determine whether covenants are dependent or independent, owing to the obscurity in which the real meaning and intent of the parties are enveloped.
When, however, it can be ascertained that the plaintiff has omitted to perform any act which constituted the consideration of the defendant’s undertaking, or any part of it, and which was to precede, in order of time, the performance of the defendant, the decisions are uniform that the plaintiff cannot recover.
In giving judgment in the case of Kingston vs. Preston (1 Doug. 690), Lord Mansfield observed: “ The dependence or independence of covenants is to be collected from the evident sense and meaning of the parties, and however transposed they may be in the deed, their precedency must depend on the order of time in which the intent of the transaction requires their performance.” Powers vs. Ware, 2 Pick. 456; Barnes vs. Maden, 2 J. R. 148; Cunningham vs. Monell, 10 J. R. 205; Smith vs. Woodhouse, 2 Penn. R. 240.
The agreement which the plaintiffs below offered in evidence was to the effect, in substance, that the defendants below were 'to sell and deliver to the plaintiffs below at their warehouse in *130Madison, one thousand bushels of wheat of a certain description, for a stipulated price; the plaintiffs below to furnish bags for hauling it, and to pay for the wheat as it was delivered by the load, except the sum of $200, which was paid at the time of the execution of the contract.
It will be seen that the parties fixed with certainty the time when the money was to be paid; and the use to which the bags were to be applied, shows beyond dispute that they were to be furnished before the wheat was to be delivered. It seems clear, then, that if the undertaking of the plaintiffs below to furnish the bags constituted any part of the consideration for the promise of the defendants below to sell and deliver the wheat, the plaintiffs should have been prepared to show that this part of the agreement had been performed on their part. It can make no difference that the thing to be done was trivial, or that it made no material difference with the defendants whether the bags were furnished or not, because when the liability of the defendant is contingent upon the performance of certain acts by the plaintiff, the latter must show a complete performance, or he cannot recover. The question, then, is, whether the agreement of the plaintiffs to furnish the bags constituted any part of the consideration of the defendants for the sale and delivery of the .wheat. We are of the opinion that it did.
We cannot doubt that this fact entered into the calculations of the parties when they made the contract, and influenced them when they fixed upon the price which the plaintiffs below were to pay for the wheat.
We are of the opinion, therefore, that the judge erred in the instructions which he gave to the jury upon this subject.
The counsel for the defendants in error contend, that although .the judge may have committed an error, yet the testimony shows that the bags weie in fact furnished by the plaintiffs below, and that the judgment should not be reversed because the error worked no injury to the defendants.
We do not desire to express any opinion upon the subject of the testimony, and shall not do so. But even if in our opinion the testimony was of the character contended for by the der *131fendants in error, we should be compelled to reverse tbe judgment on another ground.
It appears by the bill of exceptions, that the witness Herring was asked by the counsel for the defendants below, whether he had made a wager with any person that the plaintiffs would recover in this suit, and'that the judge decided that the question was improper, and that in consequence of this ruling the witness did not answer the interrogatory. We are of the opinion that this was a proper question to be propounded to the witness.'' On the cross-examination of a witness, anything which shows his friendship or'enmity to either of the parties to the suit is commonly a proper subject of inquiry. So also is anything which tends to show that, in the circumstances in which he is placed, he has a strong temptation to swear falsely. It is to be remembered that the jury are the sole judges of the credibility of the witness, and that whatever tends to assist them in the judgment which they are to form upon this subject ought not to be withheld from them. Monaghan vs. Thompson, 9 Watts & Sergt. 54. The right of counsel- to cross-examine a witness upon these subjects must, of course, be restrained within reasonable limits, and must commonly be exercised, subject to the discretion of the judge before whom the cause is tried; but when a question is propounded, with a view to show that the witness has conducted himself very improperly in relation to the suit, on the trial of which he is called to testify, we think the ruling of the judge, by which inquiry into the subject is prevented, is so erroneous as to justify a reversal of the judgment.
We shall not, of course, be understood as deciding that the wager which the witness may have made, created any pecuniary interest which would have prevented him from testifying. We only decide that the question which was asked him was proper, for the purpose of impairing his credit with the jury, and that the judge committed an error in denying to the counsel for the plaintiffs in error the right to insist upon an answer.-
For the reasons above given, the judgment of the Circuit Court must be reversed.