Sunan an-Nasa'i, Hadith 2472 ⓘ
It was narrated from Abu Hurairah that the Prophet said: "The Muslim does not have to pay Sadaqah on his slave or his horse."
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَمَّادٌ، عَنْ خُثَيْمِ بْنِ عِرَاكِ بْنِ مَالِكٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ " لَيْسَ عَلَى الْمُسْلِمِ صَدَقَةٌ فِي غُلاَمِهِ وَلاَ فِي فَرَسِهِ " .
also referenced under: Book 23, Hadith 0 (In-Book) & Volume 3, Book 23, Hadith 2474 (DarusSalam)