Sunan an-Nasa'i, Book 26, Hadith 134 (In-Book) ⓘ
It was narrated from Hajjaj bin Hajjaj that his father said: "I said: 'O Messenger of Allah, how can I pay back the dues of the one who breast-fed me?' He said: 'By giving a male or female slave.'"
أَخْبَرَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا يَحْيَى، عَنْ هِشَامٍ، قَالَ وَحَدَّثَنِي أَبِي، عَنْ حَجَّاجِ بْنِ حَجَّاجٍ، عَنْ أَبِيهِ، قَالَ قُلْتُ يَا رَسُولَ اللَّهِ مَا يُذْهِبُ عَنِّي مَذَمَّةَ الرَّضَاعِ قَالَ " غُرَّةُ عَبْدٍ أَوْ أَمَةٍ " .
also referenced under: Hadith 3329 (Reference) & Volume 4, Book 26, Hadith 3331 (DarusSalam)