Question
Is it permissible to start the prayer with Bismillah instead of Takbir?
Answer
Yes, it is permissible with dislike; because the obligation in the takbir is glorification, and the requirement is the phrase "Allahu Akbar". If he said instead of the takbir: "Allah is greater", or "Allah is more exalted", or "The Most Merciful is greater", it would suffice him, but he must perform a prostration of forgetfulness for neglecting the obligation. See: Tuhfat al-Muluk, p. 76.