What is the ruling on praying behind an Imam who commits an obvious grammatical error (lahn jali) that changes the meaning in parts other than Al-Fatihah? Is it permissible to step forward to lead the prayer in his place, or to complete the prayer individually, or to repeat it after completing it with him, if the Imam insists on his error which has fundamentally altered the meaning?

If the Imam makes a grammatical error (laḥn) in a part of the prayer other than the Fatiha, and this error alters the meaning, but he did not do so intentionally, then his prayer and the prayer of those behind him are valid, and there is no prescribed re-performance of the prayer. However, if he did so intentionally, then his prayer is invalid, as is the prayer of those behind him. It is permissible to separate oneself from the Imam with the intention of completing the prayer individually, according to some scholars. Correcting the Imam (al-fatḥ ‘ala al-Imam) is obligatory in the Fatiha, and in other parts if the error corrupts the meaning.