Going into ruku‘ or sajda before the imam

Question

If someone goes into ruku‘ or sajda before the imam, will his prayer be valid or not?

Answer

Doing so is makruh. However, if the imam also reached [him] in that ruku‘ or sajda, the prayer will be valid. But if this muqtadi raised his head before the imam reached the ruku‘ or sajda — that is, he did not share the ruku‘ and sajda with the imam at all — his prayer has become fasid (invalid)

Source: Fatawa Mahmudiyya

Preview. The full text opens with JavaScript enabled.