Musnad Ahmad 1015:18

'Ali ibn Ishaq narrated to us, 'Abdullah informed us, Ma'mar informed us, from Yahya ibn Abi Kathir, from Zayd ibn Salam, from his grandfather Mamtur, from a man among the companions of the Prophet (peace and blessings of Allah be upon him) who said: I think it is Abu Malik al-Ash'ari, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "And I command you with five things that I have been commanded with: hearing and obeying, the community (al-jama'ah), the migration (al-hijrah), and striving (al-jihad) in the way of Allah. Whoever departs from the community by the span of a hand has cast off the yoke of Islam from his neck. And whoever calls with the call of pre-Islamic ignorance (jahiliyyah) is among the heap of Hell." A man said: "O Messenger of Allah, even if he fasts and prays?" He said: "Yes, even if he fasts and prays. But call yourselves by the name of Allah, by which He named you: the servants of Allah, the Muslims, the believers."