Sunan an-Nasa'i, Volume 5, Book 44, Hadith 4661 (DarusSalam) ⓘ
it was narrated from 'Abdullah that: the Messenger of Allah forbade selling loyalty or giving it away.
أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا خَالِدٌ، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ عَبْدِ اللَّهِ، رضى الله عنه أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى عَنْ بَيْعِ الْوَلاَءِ وَعَنْ هِبَتِهِ .
also referenced under: Hadith 4657 (Reference) & Book 44, Hadith 209 (In-Book)