Musannaf Ibn Abi Shaybah

Hazrat Kulayb narrates that when Hazrat Abdullah bin Yazid Khatmi would raise his head from bowing (ruku‘), he would say the takbeer while bending down, as if descending from a sloping plank; he would go into prostration (sajdah) in this manner.

Hazrat Aswad narrates that Hazrat Umar used to say "Sami' Allahu liman Hamidah" before straightening his back after rising from ruku. And when he said the takbeer, he used to say it while bowing down.

Ibrahim says that when you bow down for prostration, say the takbeer, and when you bow down for rukoo', also say the takbeer.

Hazrat Aswad narrates that Hazrat Umar used to say the takbeer when bowing down for prostration.

Ibrahim narrates that when Hazrat Umar said "Sami' Allahu liman hamidah," he would bow down while saying the takbeer.