Mishkat al-Masabih

Al-Harith al-Ash‘ari reported God's Messenger as saying, “I command you five things: to maintain the community, to listen, to obey, to emigrate, and to fight in God's path. He who secedes from the community as much as a span has cast off the tie of Islam from his neck unless he returns, and he who summons to what the pre-Islamic people believed belongs to the assemblies of jahannam even if he fasts, prays, and asserts that he is a Muslim.” Ahmad and Tirmidhi transmitted it.