Musannaf Ibn Abi Shayba 3:6474

Waki' narrated to us, he said: Al-A'mash narrated to us, from Ibrahim, from Al-Aswad, who said: I heard Umar saying: "When he begins the prayer: 'Glory be to You, O Allah, and with Your praise, and blessed is Your name, and exalted is Your majesty, and there is no god other than You.'" Al-Aswad said: "He used to make us hear it."