The ruling on completing the mahr for a sister when the other sisters are not included

Question:
The questioner says: I have several daughters, and I have married off some of them. One of them, when her marriage contract was concluded, left the determination of the mahr to the groom's father. He set a mahr lower than the mahr I had set for her sisters, whose marriage contracts were concluded after that daughter. I had promised the one with the lower mahr that I would complete the difference for her compared to her sisters. Is it permissible for me to give her that amount without giving it to the other daughters? I should mention that I have daughters who have not yet married. If I give this daughter the difference, which is twenty thousand riyals, am I required to give the same amount to all the daughters, including those who have not yet married?

Answer:
First, the mahr is the responsibility of the husband, not the father. It is not the father's responsibility. So you must inform the husband that her mahr is less than her sisters' mahr. If he completes it, fine; otherwise, you complete it. You are not required to give to all the daughters whose weddings have not yet taken place. This is because if the cause exists, you give each one what you gave the other when the cause occurs, meaning when the marriage takes place. As for the young one whose wedding has not taken place, no, you do not give to her. Yes.

The presenter:
May Allah reward you.