As for the reverse case—when the imam is engaged in a voluntary prayer while the follower needs to perform an obligatory one—the most common example occurs in Ramadan: a person arrives after missing the ‘Ishā’ prayer and finds the congregation already praying Tarāwīḥ. Should he join them intending ‘Ishā’, or should he perform the obligatory prayer alone and then join Tarāwīḥ? The scholars are divided on this issue.

Some say it is not valid to perform an obligatory prayer behind someone who is praying a supererogatory prayer, arguing that the obligatory act ranks higher than the imam’s own prayer. Others say it is valid, because the Sunnah provides evidence for it. Muʿādh ibn Jabal (may Allah be pleased with him) used to pray the night prayer with the Prophet (peace and blessings be upon him) and then go to his people and lead them in that same prayer. For him it counted as a voluntary prayer, while for them it was obligatory, and the Prophet (peace and blessings be upon him) did not censure him.

If someone objects, “Perhaps the Prophet (peace and blessings be upon him) was unaware of this,” the reply is: if he did know, the proof is conclusive, for Muʿādh ibn Jabal (may Allah be pleased with him) was actually complained about to the Messenger (peace and blessings be upon him) for lengthening the night prayer, so it is most likely—Allah knows best—that the Prophet (peace and blessings be upon him) was informed of the entire matter. And if we assume that the Messenger of Allah (peace and blessings be upon him) did not know that Muʿādh prayed with him and then led his people, the Lord of the Messenger (peace and blessings be upon him)—Allah, Exalted and Glorified—certainly knew, for nothing in the heavens or on earth is hidden from Him. Since Allah knew and sent down no revelation disapproving this practice, that indicates its permissibility, because Allah, the Most High, would never leave His servants upon