If one prays a voluntary prayer while sitting, is it obligatory for him to be standing when he says the takbir of ihram?

Question:
He says: Honorable Shaykh, may Allah grant you success, regarding the takbir of ihram, if it is in a voluntary prayer, is it obligatory that it be done while standing?

Answer:
No, standing is not a condition for the voluntary prayer. One may pray while sitting even if he is able to stand, but he will receive half the reward of the one who stands, as stated in the hadith.