Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: When the Prophet (peace and blessings be upon him) encamped near Ta'if, he ordered a caller, who announced: Any slave who comes out will be deemed free. So two slaves came out to him, and he declared both of them free.
Al-Tabarani recorded it; its chain contains a narrator, Ibrahim bin Uthman Abu Shaybah, who is matruk (abandoned).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب العتق / 7271