Abu Thawr said: If it is from the perspective of trade, it is permissible, and if it is from other than that, it is not permissible. If he provides a guaranty with the permission of his master, it is valid; because if his master had permitted him to engage in disposal, it would be valid. The Qadi said: The analogy of the school (madhhab) is that the wealth is attached to his person (raqaba). Ibn Aqil said: The apparent view of the school and its analogy is that it attaches to the liability (dhimma) of the master. Abu al-Khattab said: Does it attach to his person or the liability of his master? There are two narrations, just like his incurring of debt with his master's permission. The discussion regarding that has already passed. If his master permits him to provide a guaranty so that the payment comes from the wealth in his hand, it is valid, and what is in his liability becomes attached to the [person of the wealth] in the slave's hand, like the attachment of the right of a crime (jinaya) to the person of the perpetrator, just as if a free person said: "I have guaranteed the debt for you, on the condition that you take it from this wealth of mine." It is valid. As for the mukatab (contracted slave), his guaranty is not valid without his master's permission, like the absolute slave (qinn), because it is a donation involving the undertaking of wealth, so it resembles his vowing charity with no wealth. It is possible that it is valid and he is pursued for it after his manumission, as per our statement regarding the slave. If he provides a guaranty with his [master's] permission, there are two views; one of them is that it is also not valid, because it might lead to the loss of freedom. The second is that it is valid, because the right belongs to both of them and does not exit from them. As for the sick person, if his illness is not life-threatening, or is not the death-illness, his ruling is that of the healthy person. If it is the life-threatening death-illness, the ruling on his guaranty is the ruling on his donation; it is counted from his third, because it is a donation involving the undertaking of wealth that is not binding upon him, and he did not receive compensation for it, so it resembles a gift. If the sign language of a mute is understood, his guaranty is valid; because his sale, acknowledgment, and donation are valid, so his guaranty is valid, just like that of one who speaks. The guaranty is not established by his writing alone, separate from signs through which it is understood that he intended the guaranty; because he might write in jest or for testing, so the guaranty is not established with the possibility [of such intent]. As for one whose signs are not understood, a guaranty is not valid from him; because he does not intend by his guaranty [anything], and because his other disposals are not valid, so his guaranty is likewise.