This point is overlooked by many people, including some students of sacred knowledge. They assume that if you have paid for one child’s wedding, you are obliged to bequeath the younger children a sum equal to what you spent. That is not correct, for any bequest made to an heir is absolutely impermissible.

If, however, someone—out of ignorance—does leave a bequest in favor of an heir, the matter passes to the heirs after his death: if they wish, they may execute the bequest; if they wish, they may annul it.

Third: the permissible waṣiyyah. This is when a person bequeaths part of his estate not exceeding one-third, for going beyond one-third is forbidden. Anything below that limit is at your discretion: you may bequeath it to whomever you wish, except the heirs—and such a bequest is lawful.

Which, then, is better: a third, a quarter, or less than that? We say: do not exceed one-third, but whatever is less than one-third is preferable. Ibn ʿAbbās—may Allah be pleased with them both—said, “If people would reduce the third to a quarter…,” for the Prophet ﷺ told Saʿd ibn Abī Waqqāṣ, “A third—and a third is much.” Abū Bakr—may Allah be pleased with him—bequeathed one-fifth of his wealth, saying, “I am content with what Allah chose for Himself: one-fifth.” Thus he left one-fifth of his estate, and that is the most excellent course.

It would be well if students of knowledge and those who draft wills would advise testators that the optimal bequest is one-fifth, not one-third. Among the people, one-third has become the common figure, yet it is only the upper limit set by the Messenger ﷺ, and whatever falls below it is better.