The ruling on a latecomer saying the opening takbir while bending for ruku'

Question:
We also received this question from our brother Abu 'Abdullah. He says: Shaykh, if I say the opening takbir while bending, but I am closer to standing upright than to ruku', is my prayer valid, or does it become a voluntary prayer? And what are the circumstances, Shaykh, in which an obligatory prayer becomes a voluntary one?

Answer:
My brother, if you mean that you are a latecomer and you arrive while the imam is in ruku', it is not permissible for you to delay the opening takbir until you bend for ruku'. You must say it while standing upright, then bend after the opening takbir. As for an obligatory prayer becoming a voluntary one, if one intends that, if one intends to turn the obligatory prayer into a voluntary one, because the voluntary is less than the obligatory, then it is permissible for him to do so. Yes.