Musnad Ahmad 937:270

Abdullah narrated to us, Ahmad ibn Muhammad narrated to us, Abu Bakr—meaning Ibn Ayyash—narrated to us, from Mutarrif, from Abu al-Jahm, from Khalid ibn Wahban, from Abu Dharr, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever separates from the community by a span, he has cast off the yoke of Islam from his neck."