Sunan Ibn Majah Book 20, Hadith 3
“Whoever changes his religion, execute him.”
“It is not lawful to shed the blood of a Muslim who bears witness that none has the right to be worshiped but Allah (SWT), and that I am the Messenger of Allah (ﷺ), except in one of three cases: a soul for a soul; a married person who commits adultery, and one who leaves his religion and splits from the Jama`ah.”
“Allah (SWT) will not accept any good deed from a polytheist who committed polytheism after having become Muslim, until he leaves the polytheists and joins the Muslims.”