What is the ruling on the prayer of the ma'mum if he says the takbir before the imam?

The questioner : Shaykh, may Allah bless you. This is a ma'mum who said the takbir of ihram before his imam, then continued the prayer and said the taslim with the imam, but he said the takbir of ihram before the imam?

The Shaykh : He must repeat the prayer. He has to repeat the prayer because his prayer was not valid.

The questioner : Is his prayer considered that of a person praying alone, O Shaykh?

The Shaykh : No, because he intended to follow this man. How can he be considered a person praying alone? Yes, after you, please.