´It was narrated that Anas said:` "Abu Talhah proposed marriage to Umm Sulaim and she said: 'By Allah, a man like you is not to be rejected, O Abu Talhah, but you are a disbeliever and I am a Muslim, and it is not permissible for me to marry you. If you become Muslim, that will be my dowry, and I will not ask you for anything else.' So he became Muslim and that was her dowry." (one of the narrators) Thabit said: "I have never heard of a woman whose dowry was more precious than Umm Sulaim (whose dowry was) Islam. And he consummated the marriage with her, and she bore him a child."
Hadith Referenceسنن نسائي / كتاب النكاح / 3343
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:إسناده صحيح
1؎: That is, after embracing Islam, I will not demand the prompt (mu‘ajjal) dower (mahr).
Explanation & Benefits
Hafiz Muhammad Ameen
This hadith is explicit that there was no dowry (mahr) other than Islam. Thus, if the woman is agreeable, such a religious benefit can also constitute a dowry (mahr). It is not necessary for it to be material wealth.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 3343