Whoever separates from the community by a handspan has removed the noose of Islam from his neck

It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever leaves the Jama'ah even by the measure of a handspan has cast off the collar of Islam from his neck."
Jarir bin Abd al-Hamid has corroborated it as well.

It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever opposes the Jama'ah of the Muslims even by the measure of a handspan has removed the ring of Islam from his neck."
Khalid bin Wahban is a well-known Tabi'i against whom there is no criticism, but the two Shaykhs did not narrate from him.

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever goes out from the Jama'ah even by the measure of a handspan has cast off the collar of Islam from his neck until he returns," and he said: "Whoever dies while there is no Imam of the Jama'ah over him, his death is a death of Jahiliyyah (pre-Islamic ignorance)."
This text is narrated with a sahih chain on the condition of the two Shaykhs.

It is narrated from al-Harith al-Ash'ari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "I command you with five things that Allah has commanded me with: (holding to) the Jama'ah, listening, obeying, Hijrah (emigration), and Jihad in the path of Allah. So whoever goes out from the Jama'ah even by the measure of a handspan has cast off the collar of Islam from his head, unless he returns."

It is narrated from al-Harith al-Ash'ari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Indeed, Allah has commanded me with five things which I act upon" (then he mentioned the whole lengthy hadith).
Mu'awiyah bin Sallam and Aban bin Yazid al-Attar have also narrated it in the same way from Yahya bin Abi Kathir.

It is narrated from al-Harith al-Ash'ari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Indeed, Allah Almighty commanded Yahya bin Zakariya (peace be upon him) with five things, and said that he should act upon them himself and command the Children of Israel to act upon them"; then he mentioned the whole hadith, and in it is also that he (peace and blessings be upon him) said: "Indeed, Allah has commanded me too with five things" (then he mentioned the whole lengthy hadith).
This hadith is sahih according to the principles we have laid down concerning the Companions, that even if only one narrator is found from a Companion, it is still accepted; for al-Harith al-Ash'ari is a well-known Companion, and Imam Yahya bin Ma'in has also confirmed his being a Companion.