Sunan an-Nasa'i, Book 26, Hadith 145 (In-Book) ⓘ

It was narrated that Anas said: "Abu Talhah married Umm Sulaim and the dowry between them was Islam. Umm Sulaim became Muslim before Abu Talhah, and he proposed to her but she said: 'I have become Muslim; if you become Muslim I will marry you.' So he became Muslim, and that was the dowry between them."

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ مُوسَى، عَنْ عَبْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ أَبِي طَلْحَةَ، عَنْ أَنَسٍ، قَالَ تَزَوَّجَ أَبُو طَلْحَةَ أُمَّ سُلَيْمٍ فَكَانَ صَدَاقُ مَا بَيْنَهُمَا الإِسْلاَمَ أَسْلَمَتْ أُمُّ سُلَيْمٍ قَبْلَ أَبِي طَلْحَةَ فَخَطَبَهَا فَقَالَتْ إِنِّي قَدْ أَسْلَمْتُ فَإِنْ أَسْلَمْتَ نَكَحْتُكَ ‏.‏ فَأَسْلَمَ فَكَانَ صَدَاقَ مَا بَيْنَهُمَا ‏.‏