Muwatta Imam Malik (Riwayat Yahya)

Imam Malik, may Allah have mercy on him, said that if a person hires an animal with the agreement that he will go up to a certain place, and then he goes beyond that, the owner of the animal has the option: if he wishes, he may take the fare for the extra distance traveled according to the customary rate, or, if not, he may take from the renter the value of his animal on that day and at the place where it was agreed to go, and also take the fare that was previously agreed upon. If the fare was only for going, and if it was for going and returning, then he should take half of the agreed fare, because half the fare was for going and half for returning, and at the time the renter exceeded the agreement, only half the fare was due upon him. If the renter hired the animal for a round trip, and when he reached the destination the animal died, then there will be no compensation upon the renter, and the owner will receive half the fare. Similarly, if the owner of the capital forbids the agent (mudharib) from buying certain goods, and the agent buys them anyway thinking that he will guarantee it and take all the profit or loss, then the owner of the capital has the option: if he wishes, he may keep the partnership in the goods, or if he wishes, he may take back his principal. Likewise, in the case of entrusted goods (bida’ah), if the owner says to buy certain goods, and the person buys something else, then the owner has the option: if he wishes, he may consider that property as his own, or he may take back his principal.