Musannaf Ibn Abi Shaybah

Hazrat Ibn Umar (may Allah be pleased with both of them) and Hazrat Zaid bin Thabit say that if a person joins the Imam while he is in the state of bowing (ruku‘), then saying one takbeer is sufficient for him.

Hazrat Zuhri states that Hazrat Urwah bin Zubair and Hazrat Zaid bin Thabit, when joining the prayer while the Imam was in ruku, used to say only one takbeer for both ruku and the prayer.

Ibrahim says that one takbeer is sufficient for you.

Ibn ‘Ulayyah says that I asked Ibn Abi Najih whether a person may join the congregation while the people are in the state of bowing (ruku‘), so should he say one takbir and go into ruku‘? He replied that Mujahid used to say that it is permissible for him to do so.

Hazrat Ata says that one takbeer is permissible; if one says more, it is better.

Hazrat Ibn al-Musayyib says that one takbeer is permissible.

Hazrat Bakr says: Say one takbeer.

Hazrat Maymoon says that one takbeer is sufficient.

Hasan considered it preferable that a person should say two takbirs. If, due to haste or forgetfulness, only one takbir is said, it is still permissible.

Hazrat Hakam says that one takbeer is sufficient.