This varies into two types: First, that the hiring is for a specific person, such as hiring his slave for the grazing of sheep, or his son for a specific task. Second, that it is for a task in the liability (dhimma), such as the sewing of a shirt or the building of a wall. Whenever it is for a task in his liability and he falls ill, it is mandatory for him to appoint someone in his place to perform it; because it is a right that has become due in his liability, it is therefore mandatory for him to fulfill it, like an item purchased with advance payment (salam). The employer is not obligated to grant him a delay because the contract, in its absolute terms, requires immediacy, and there is harm to the employer in delay. As for if the hiring was for his specific person during a period or otherwise, and he falls ill, he does not appoint anyone else in his place, because the hiring was for his specific labor, not for something in his liability, and the labor of another is not what was contracted upon. The contract was made upon a specific person, so it is similar to if one bought a specific object, it is not permissible for him to offer another one in its place, nor to replace it, unlike if it were in the liability, for it is permissible to replace a defective item, and the contract is not voided by the destruction of what he took possession of, whereas a specific sold item is the opposite; thus is the hiring. And if the hiring was for a task in the liability, but it cannot be performed by anyone other than the hired person, such as copying, for the purpose varies according to the differences in handwriting, he is not obligated to appoint someone else in his place, and the employer is not required to accept such if the hired person offers it; because the purpose is not achieved from other than the copyist as it is achieved from him, so it is similar to if one had made a contract for a specific type, and he delivered something else. Thus is everything that varies according to differences in individuals.

Section: It is permissible to hire for the digging of wells, rivers, and canals, because it is a known benefit, and it is permissible for a man to perform it voluntarily for another, so it is permissible to contract for it in hiring, like service. It is necessary to estimate the work by a duration or a specific task. If he limits it by duration, such as saying: "I have hired you for a month to dig a well [or a river] for me," he does not need to know the amount, and he is obligated to dig during that