Paying the first wife in return for marrying another

Q 1: In our village, we follow a tradition which we do not know whether it is a custom or an act of `Ibadah (worship). When a man marries a second wife, he is required - and sometimes even forced - to give his first wife a sum of money, gold or what is equal to one fourth of the Mahr (mandatory gift to a bride from her groom) of the second wife, in order to please her. What is the ruling on this act? If it is Mashru` (Islamically acceptable), what is the evidence?

A: If a man marries a second wife, he is not obligated to give anything to his first wife; and no one should force him to do so. However, he may willingly give his first wife whatever amount he wishes as a way of honoring her and maintaining their good relationship. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.