Should the Muqtadi follow the Imaam or Complete the Tashahhud?

Q: Salaah-647: The lmaam has completed the Tashahhud in the first Qa'dah and gets up for the third Rakaahs whereas the Muqtadi has still not yet recited the Tashahhud. Should he follow the Imaam or first complete the Tashahhud?

Answer: As far as possible, the Muqtadi should first complete the Tashahhud before standing up. However, the salaah will still be valid if he follows the Imaam (without completing the Tashahhud). And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2