What is the Shar'i ruling on the action of a father who wrote his properties to his male children, with the condition that a small amount be paid to their female sisters, while the largest share of the properties' value came from the mother's money? And is it permissible for the son to intervene to correct this matter, knowing that the parents are saving money to perform 'Umrah despite their old age and illness?

It is obligatory to equalize gifts among children, based on the prophetic tradition that stipulates this, except in the presence of a legitimate justification for favoritism. This could be if one of the children has a large family, is a student of knowledge, or is ill and requires treatment. There is no objection to preferring some individuals who are not one's own children over others. Based on this, a mother may give a gift to her husband's sons without giving to his daughters, and she is not obliged to equalize except among her direct children. As for the father, he must equalize among all his children. To apply these rulings, it is necessary to determine the share of the houses owned by both the father and the mother.