Al-Adab Al-Mufrad, Book 4, Hadith 80 (English) ⓘ

Musa ibn 'Ali reported that the Prophet, may Allah bless him and grant him peace, said, "Shall I show you the greatest sadaqa (or one of the greatest forms of sadaqa)?" He replied, "Yes, indeed, Messenger of Allah!" He went on, "To provide for your daughter when she is returned to you and you are her sole source of provision."

حَدَّثَنَا عَبْدُ اللهِ بْنُ صَالِحٍ قَالَ‏:‏ حَدَّثَنِي مُوسَى بْنُ عَلِيٍّ، عَنْ أَبِيهِ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ لِسُرَاقَةَ بْنِ جُعْشُمٍ‏:‏ أَلاَ أَدُلُّكَ عَلَى أَعْظَمِ الصَّدَقَةِ، أَوْ مِنْ أَعْظَمِ الصَّدَقَةِ‏؟‏ قَالَ‏:‏ بَلَى يَا رَسُولَ اللهِ، قَالَ‏:‏ ابْنَتُكَ مَرْدُودَةٌ إِلَيْكَ، لَيْسَ لَهَا كَاسِبٌ غَيْرُكَ‏.‏