Mishkat al-Masabih #3081
Marriage
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
وَعَنْ أَنَسٍ قَالَ: تَزَوَّجَ أَبُو طَلْحَةَ أُمَّ سُلَيْمٍ فَكَانَ صَدَاقُ مَا بَيْنَهُمَا الْإِسْلَامَ أَسْلَمَتْ أُمُّ سُلَيْمٍ قَبْلَ أَبِي طَلْحَةَ فَخَطَبَهَا فَقَالَتْ: إِنِّي قَدْ أَسْلَمْتُ فَإِنْ أَسْلَمْتَ نَكَحْتُكَ فَأَسْلَمَ فَكَانَ صدَاق مَا بَينهمَا. رَوَاهُ النَّسَائِيّ
Anas said that Abu Talha married Umm Sulaim, the dower between them being acceptance of Islam. Umm Sulaim had become a Muslim before Abu Talha, and when he asked her in marriage she said, "I have become a Muslim, so if you become one I shall marry you.” He then accepted Islam and that was the dower arranged between them.
Nasa’i transmitted it.
About Mishkat al-Masabih
This hadith is #3081 from Mishkat al-Masabih, in the Book of Marriage.