Musannaf Ibn Abi Shaybah 22044 — A man who is obliged to free a slave

Abu Abdullah al-Jisri said: I said to Sayyiduna Ma'qil bin Yasar (may Allah be pleased with him): A man among us wishes to buy a slave in order to free him; what method should he adopt? He said: When you buy a slave with the intention of freeing him, do not buy him by mentioning the emancipation to his owner, for that is a knot of slavery; rather, buy him silently, and then, if you wish, keep him, and if you wish, free him.