Musannaf Ibn Abi Shaybah

Ibrahim and Hasan say that when a person recites a verse of prostration, he should say ALLAHU AKBAR while raising his head and while performing the prostration.

Hazrat Abu Qilabah and Hazrat Ibn Sirin state that when a person recites a verse of prostration outside of prayer, he should say ALLAHU AKBAR.

Hazrat Abdullah bin Muslim narrates that when my father would recite a verse of prostration, he would say ALLAHU AKBAR and then perform the prostration.

Hazrat Ata bin Saib says that when Hazrat Abu Abdur Rahman would recite a verse of prostration while walking, he would say takbeer and bow down in the direction his face was turned, and then while raising his head, he would also say takbeer.

Hazrat Aamir says that when you recite a verse of prostration, say Takbeer.