Musannaf Ibn Abi Shayba 3:197

Abu Bakr narrated to us, he said: Muhammad ibn Bishr narrated to us, he said: Sa'id narrated to us, from Qatadah, from Mutarrif ibn 'Abd Allah ibn al-Shikhkhir, from 'Aishah, that the Prophet, peace and blessings of Allah be upon him, used to say in his bowing (ruku') and his prostration (sujud): "Subbuh, Quddus, Rabb al-Mala'ikah wa al-Ruh" (Glorified, Holy, Lord of the angels and the Spirit).