Is a father's equality among his children in distributing his salary considered an injustice to the eldest among them, or does he have the freedom to do so?

Justice must be observed among children in gifts and endowments, as stated in the Hadith: "Fear Allah and be just among your children."

As for maintenance (nafaqah), each child should be given according to their sufficiency and need, not with absolute equality. The maintenance of an older child is not like that of a younger one, and the maintenance of a student is not like that of others, and the maintenance of one who needs to get married is not like that of one who does not. Adjustment in maintenance is by giving each of them what they need.

What the father does by giving to the children equally is an error, because anything exceeding the maintenance for sufficiency is considered a gift, and justice is required in it, not equality.

As for gifts to wives, he may give them whatever he wishes and make them equal.

The father should be advised to clarify the difference between maintenance and gifts, and the prohibition of injustice in giving gifts among children. If he provides for their sufficiency, he may then distribute what remains justly.