It is narrated from Sayyiduna Mu'awiyah bin Haydah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever changes his religion, Islam, and becomes an apostate, kill him. Allah Almighty does not accept the repentance of a servant who disbelieves after accepting Islam."
Al-Tabarani (may Allah have mercy on him) recorded it, and all its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الحدود والديات / 10573M