Musnad Ahmad 5:7

Abu Sa’id narrated to us, Isra’il narrated to us, ‘Abd al-A’la narrated to us, from Abu ‘Abd al-Rahman, from ‘Ali, may Allah be pleased with him, who attributed it to the Prophet (marfu’an), he said: "Whoever lies about a dream he has seen, he will be tasked with tying a knot in a barley grain on the Day of Resurrection."