Muwatta Imam Malik (Riwayat Yahya)

It is narrated from Amr bin Salim Zarqi that it was said to Sayyiduna Umar bin Khattab, may Allah be pleased with him, that there is a boy in this place in Madinah who is near puberty but has not yet reached it, from the tribe of Ghassan, and his heirs are in Syria, and he has wealth, and here he has no heir except a paternal cousin (female). So Sayyiduna Umar bin Khattab, may Allah be pleased with him, said: Let him make a will. The boy made a will for the wealth, which was called Bir Jashm, in favor of his paternal cousin (female). Amr bin Salim said: That wealth was sold for thirty thousand dirhams. And his paternal cousin (female) was the mother of Amr bin Salim.

It is narrated from Abu Bakr bin Hazm that a boy from Ghassan was about to die in Medina, and his heirs were in Syria. This was mentioned to Sayyiduna Umar, may Allah be pleased with him, and he was asked: Should he make a will? Sayyiduna Umar, may Allah be pleased with him, said: He should make a will. Yahya bin Saeed said: The boy was either ten or twelve years old, and he left behind (property called) Bi’r Jashm, and he made a will for it. People sold it for thirty thousand dirhams.

Imam Malik, may Allah have mercy on him, said: In our view, this ruling is agreed upon that the will (wasiyyah) of a weak-minded, foolish, or insane person who sometimes regains sanity is valid, when he has enough understanding to comprehend the will he is making. If he does not have even this much understanding, then his will is not valid.