Hadithcore
Sahih al-Bukhari, 6753
sahih

Narrated `Abdullah:

The Muslims did not free slaves as Sa'iba, but the People of the Pre-lslamic Period of Ignorance used to do so.

حَدَّثَنَا قَبِيصَةُ بْنُ عُقْبَةَ، حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي قَيْسٍ، عَنْ هُزَيْلٍ، عَنْ عَبْدِ اللَّهِ، قَالَ إِنَّ أَهْلَ الإِسْلاَمِ لا يُسَيِّبُونَ، وَإِنَّ أَهْلَ الْجَاهِلِيَّةِ كَانُوا يُسَيِّبُونَ‏.‏

References2 variants
In-Book Reference
Book 85, Hadith 30
USC-MSA web (English) reference
Vol. 8, Book 80, Hadith 745 (deprecated numbering scheme)