Musannaf Ibn Abi Shayba 3:1811

Ibn Fudayl narrated to us, from ‘Ata’ ibn al-Sa’ib, from Abu ‘Abd al-Rahman, that he used to recite [Surat] al-Sajdah while he was walking. He would say "Allahu Akbar" and gesture [for prostration] in whichever direction his face was turned, and he would say "Allahu Akbar" when he raised his head.