Musannaf Ibn Abi Shayba 3:4026

Abu Bakr narrated to us, he said: Abdullah bin Numayr narrated to us, from Hajjaj, from Amr bin Murrah, from Abu Ubaydah, he said: There is no one more averse to speaking after the two rak'ahs of Fajr until he prays the morning prayer than Ibn Mas'ud.