Musnad Ahmad 351

Abu ‘Abd Allah Muhammad ibn Ja‘far narrated to us; Shu‘bah narrated to us, from al-Hakam, from ‘Umarah ibn ‘Umayr, from Ibrahim ibn Abi Musa, from Abu Musa: He used to give legal opinions in favor of tamattu‘. A man said to him, ‘Hold back on some of your legal opinions, for you do not know what the Commander of the Faithful has instituted in the rites after you.’ Later he met him and asked him. ‘Umar, may Allah be pleased with him, said, ‘I know that the Prophet, peace and blessings be upon him, practiced it, as did his Companions. But I disliked that they should spend the night with their wives beneath the arak trees, then set out for Hajj with their heads dripping.’