Musannaf Ibn Abi Shaybah

Hazrat Aswad narrates that Hazrat Abdullah bin Mas'ud (may Allah be pleased with him), when he finished the recitation, would say Takbeer, then recite the Du'a Qunoot, and when he finished Qunoot, he would say Takbeer and go into Ruku.

Ibrahim says that when you intend to recite the Qunoot supplication, then say the takbeer for Qunoot, and when you intend to bow (for ruku‘), then also say the takbeer.

When Ibrahim would recite the Qunoot, he used to say the Takbeer, and when he finished, he would say the Takbeer again.

Ibrahim says that when you finish the recitation, say the takbeer, and when you finish the qunoot, then again say the takbeer and perform the bowing (ruku).

Hazrat Shu’bah says that I heard Hazrat Hakam, Hazrat Hammad, and Hazrat Abu Ishaq saying that in the Witr prayer’s Qunoot, when you finish the recitation, say Takbeer and then recite the Du’a Qunoot.