It is narrated from Sayyiduna Abu Malik al-Ash'ari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Allah, the Mighty and Majestic, has commanded me to command you with five things: hold fast to jihad, listening, obedience and emigration. Whoever separates from the community even by the length of a bow, neither his prayer nor his fasting will be accepted, and such people are the very fuel of the Fire."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3455