This is what many people praying behind an imam do when they consider reciting al-Fātihah while he recites aloud to be obligatory or recommended. They make his recitation difficult and confuse him, while also preventing those nearby from listening attentively as they have been commanded. They thus defeat both the purpose of the imam’s reciting aloud and the purpose of those behind him listening. Clearly, such conduct is disliked.
Moreover, if all those praying behind him were reciting, his recitation aloud would have no listener and would therefore serve no purpose. Nor would there be any benefit in his instruction, “When he says Āmīn, say Āmīn.” They would be saying Āmīn to a recitation of the Quran that they had not listened to—that none of them had listened to—unless it were argued that the imam must pause long enough for them to recite. Yet they do not regard a pause long enough for this recitation as obligatory; they merely recommend it. It is therefore clear that recommending the pause accords with recommending recitation during it. If recitation were obligatory for those praying behind the imam, he would have to pause long enough for it, either engaging in remembrance of Allah during that pause or remaining completely silent. I know of no one who has made such a pause obligatory for the sake of those reciting behind the imam.
This is further confirmed by the fact that he made listening silently obligatory while the imam recites, as related in Sahīh Muslim from Abū Mūsā, who said:
“The Messenger of Allah, may Allah bless him and grant him peace, addressed us, explained to us our prescribed practice, and taught us how to pray. He said, ‘Straighten your rows, then let one of you lead you in prayer. When he pronounces the takbīr, pronounce the takbīr, and when he recites, listen silently.’”
He also narrated it from Abū Hurayrah, who reported that the Messenger of Allah said: