Sunan Abi Dawud, Hadith 5121

Kulaib b. Manfa'ah said that his grandfather told then he went to the Prophet and said: Messenger of Allah! to whom should I show kindness? He said: Your mother, your sister, your brother and the slave whom you set free and who is your relative, a due binding (on you), and a tie of relationship which should be joined.

حَدَّثَنَا مُحَمَّدُ بْنُ عِيسَى، حَدَّثَنَا الْحَارِثُ بْنُ مُرَّةَ، حَدَّثَنَا كُلَيْبُ بْنُ مَنْفَعَةَ، عَنْ جَدِّهِ، أَنَّهُ أَتَى النَّبِيَّ صلى الله عليه وسلم فَقَالَ يَا رَسُولَ اللَّهِ مَنْ أَبَرُّ قَالَ ‏ "‏ أُمَّكَ وَأَبَاكَ وَأُخْتَكَ وَأَخَاكَ وَمَوْلاَكَ الَّذِي يَلِي ذَاكَ حَقٌّ وَاجِبٌ وَرَحِمٌ مَوْصُولَةٌ ‏" ‏ ‏.‏

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also referenced under: Hadith 5140 (DarusSalam)