Musannaf Ibn Abi Shayba 3:4060

Abu Mu'awiyah narrated to us, from al-A'mash, from al-Qasim, from his father, who said: Abdullah entered the mosque for the dawn prayer, and there were people who had leaned their backs against the Qibla. He said: "Move away from the Qibla; do not come between the angels and their prayer, for these two rak'ahs are the prayer of the angels."