Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: The Prophet (peace and blessings be upon him) said about slaves: "If they do good, accept it; if they do wrong, pardon them; and if they are beyond your control, sell them."
Al-Bazzar recorded it; its chain contains Asim bin Ubaydullah, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب العتق / 7215