Musnad Ahmad 937:280

'Abd al-Samad narrated to us, my father narrated to me, Husayn narrated to me, he said: Ibn Buraydah said: Yahya ibn Ya'mar narrated to me, that Abu al-Aswad narrated to him, from Abu Dharr, that he heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "No man accuses a man of immorality (fisq), and no man accuses him of disbelief (kufr), except that it returns upon him if his companion is not as he said."