he has young children, so he writes in his will: “I have bequeathed that each of my children who has not married be married from one-third of my estate.” This is not permissible, because marriage falls under meeting needs, and these children have not yet reached marriageable age. Thus, making such a bequest for them is forbidden, and the heirs may not carry it out either—except for any heir who is an adult and legally competent and who permits it; in that case, there is no objection insofar as it concerns his own share of the estate.
There are several issues here:
First: May he give preference to one of them on account of dutifulness? That is, if one is more dutiful to his parents than another, and he says, “I will give the dutiful child more than I give the undutiful one,” in order to encourage the dutiful child and urge the undutiful one to improve? This is not permissible, because the reward for dutifulness is greater than a few dirhams that one gives him. Its reward is with Allah, Mighty and Majestic is He. Moreover, you do not know: perhaps the dutiful child of today will become undutiful tomorrow, and the undutiful child of today will become dutiful tomorrow. Therefore, it is not permissible to favor him because of his dutifulness.
Second: If one of the children works with his father in his shop or on his farm, may the father give him more than the other child from whom he has derived no benefit? There is detail to this. If the child who assists his father seeks thereby the Countenance of Allah, then the father should not give him anything, because this falls under dutifulness to parents. But if he seeks compensation for it, or if his father stipulated compensation for him before he began the work, then there is no objection; however, he should be given no more than the wage he would receive were he an unrelated worker.
Third: If one of the children is a disbeliever due to apostasy, or has never entered Islam in the first place, some scholars say that equal treatment is not obligatory, because Allah, Most High, says: “Should We then treat those who submit as We treat the wicked?” [al-Qalam 68:35]
Other scholars say that equal treatment is obligatory, because this is a right whose cause is