The ruling on one who leaves out the opening takbir or says it while bowing

Question:
He says: Honorable Shaykh, may Allah grant you success. A man says: I caught up with the imam while he was bowing, so I hurried over, said Allahu Akbar, and bowed, but I left out the opening takbir, or I said the opening takbir while I was in the state of bowing. Is his prayer valid?

Answer:
It is not valid, because if he leaves out the opening takbir, he does not enter into the prayer. If he leaves out the opening takbir, he does not enter into the prayer, so his prayer is not valid. And if he says it after bending forward, it is also not valid, because the opening takbir is performed while standing, unless he is sick or unable to stand, in which case he performs it while sitting. Yes.