Prayer: Imam Mistakenly Performing Qunut or Tashahhud
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1458
If the imam mistakenly performs qunūt in a rakʿah that does not have qunūt, or if he mistakenly starts saying tashahhud in a rakʿah that does not have tashahhud, then the follower must not perform qunūt or say tashahhud. However, he cannot go into rukūʿ before the imam or stand up before the imam; rather, he must wait until the qunūt and tashahhud of the imam finish and then complete the rest of the prayer with him.