Answered by Shaykh Faraz Rabbani
When following the Imam, when should one go into ruku’, sajda etc.?
Assalamu alaikum wa rahmatullah,
It is best to follow the imam right as he begins saying “Allahu Akbar,” though doing so in a way that does not make one fall ahead of the imam. This applies to all parts of the prayer. It is especially important not to finish one’s first or second salams before the imam.
[Shurunbulali, Maraqi al-Falah]
Wassalam,
Faraz.