Musannaf Ibn Abi Shaybah

Ibrahim says that when a person forgets the Takbir-e-Tahrima, he should perform the prayer again from the beginning.

Hasan says that if a person forgets the opening takbeer (takbeer-e-tahrima), then the takbeer of bowing (ruku) is sufficient for him.

Hazrat Zuhri says about the person that if someone forgets to say Takbeer-e-Tahreema at the beginning of the prayer, then whenever he remembers, he should say the Takbeer. If he remembers after completing the prayer, the prayer is valid, because the Takbeer of Ruku is sufficient for him.

Hazrat Hammad says that if the imam forgets the Takbeer-e-Tahreema before starting the prayer, he should repeat the prayer. Hazrat Hakam says that the Takbeer of Ruku will suffice for him.

Hazrat Bakr says that when one remembers, he should say the takbeer.