he had heard a man from Ash-Sham asking Abdullah bin Umar about Tamattu after Umrah until Hajj, so Abdullah bin Umar said: "It is lawful." The man from Ash-Sham said: "But your father prohibited it." So Abdullah bin Umar said: "Is the order to follow my father or is the order (to follow) for the Messenger of Allah?" The man said: "Rather it is for the Messenger of Allah." So he said: "Indeed the Messenger of Allah did it."
Jami` at-Tirmidhi Book 9, Hadith 17