Narrated to us by Waki', narrated to us by Mis'ar, narrated to us by Ubayd ibn Hasan, from Ibn Abi Awfa, that the Prophet, peace and blessings be upon him, used to say that, and he did not say: in the prayer.
Hadith Referenceمسند احمد / تتمہ مُسْنَدِ الْكُوفِيِّينَ / 19105