Sahih al-Bukhari, Hadith 2594 ⓘ
Narrated Maimuna, the wife of the Prophet that she manumitted her slave-girl and the Prophet said to her, "You would have got more reward if you had given the slave-girl to one of your maternal uncles."
وَقَالَ بَكْرٌ عَنْ عَمْرٍو، عَنْ بُكَيْرٍ، عَنْ كُرَيْبٍ، مَوْلَى ابْنِ عَبَّاسٍ إِنَّ مَيْمُونَةَ زَوْجَ النَّبِيِّ صلى الله عليه وسلم أَعْتَقَتْ وَلِيدَةً لَهَا فَقَالَ لَهَا " وَلَوْ وَصَلْتِ بَعْضَ أَخْوَالِكِ كَانَ أَعْظَمَ لأَجْرِكِ " .
also referenced under: Book 51, Hadith 28 (In-Book) & Volume 3, Book 47, Hadith 767 (USC-MSA)