Is it lawful to stipulate an amount as a deferred Mahr?

Q: Some tribes used to ask the husband when getting married to pay an amount of money called deferred dowry. This deferred money should be paid by the husband in case of divorce. In this case, the husband is required to pay this sum of money which is different from the dowry. Is it permissible to do this according to Shari`ah (Islamic law) rulings? What is the ruling on doing so if he did not pay a dowry? If he paid a dowry, what should we do? (Part No. 19; Page No. 65) May Allah reward you well.

A: There is no harm in you doing this. This is because it is a defined sum of money and a part of the dowry. People may agree on deferring part of the dowry for a certain interest that requires doing so as using this deferred dowry as a deterrent against divorce. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.