Celsus, Digest, Book VII. Quintus Mucius Scævola says that if anyone has given security for money lent at interest, and the principal debtor, having been sued, attempts to deny that the money was lent at interest, and the surety, by paying the interest, deprives the principal debtor of the opportunity of refusing payment, he cannot recover this money from the principal debtor. If, however, the latter had notified the surety that he would refuse to pay what is due with interest, and the surety was not willing to refuse payment on account of his reputation, he can recover from the principal debtor whatever he paid on this account. This opinion Scævola thought to be well founded; for, in the former instance, the surety paid but little attention to good faith, when he appeared to deprive the principal debtor of the power to avail himself of his right; but, in the latter instance, he should not have been a source of injury to the surety if he had had any regard for his own sense of honor. 1If I direct you to transact business for me by lending money, with the understanding that you are to transfer the claim to me at my risk, and that the profit, if any, will be mine; I think that the mandate will stand. 2But if I direct you to transact the business for yourself, so that the claim will remain in your possession; that is to say, that you may lend money to anyone you please, and receive the interest, and that I alone will assume the risk; this transaction is outside the terms of the mandate, just as if I should direct you to purchase any kind of a tract of land for me.

Celsus, Digest, Book VII. If a debtor who has asked that property pledged be given him under a precarious tenure should discharge the debt, the said tenure comes to an end; as it was the intention of the parties that it should only continue to exist until the time when the debt was paid.

Celsus, Digest, Book VII. The excuse of an empty fear is not a legal one.