Hadith: Perhaps you recite behind your Imām? We said: Yes, that is so, O Messenger of Allah. He said: Do not do so except with Sūrat al-Fātihah, since the prayer is invalid for the one who does not recite it

عَنْ عُبَادَةَ بْنِ الصَّامِتِ رضي الله عنه قَالَ:

كُنَّا خَلْفَ رَسُولِ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ فِي صَلَاةِ الْفَجْرِ، فَقَرَأَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ، فَثَقُلَتْ عَلَيْهِ الْقِرَاءَةُ، فَلَمَّا فَرَغَ قَالَ: «لَعَلَّكُمْ تَقْرَؤُونَ خَلْفَ إِمَامِكُمْ؟» قُلْنَا: نَعَمْ هَذًّا يَا رَسُولَ اللَّهِ، قَالَ: «لَا تَفْعَلُوا إِلَّا بِفَاتِحَةِ الْكِتَابِ فَإِنَّهُ لَا صَلَاةَ لِمَنْ لَمْ يَقْرَأْ بِهَا».
[حسن] - [رواه أبو داود والترمذي وأحمد]

‘Ubādah ibn As-Sāmit (may Allah be pleased with him) reported: We were praying the Fajr prayer behind the Messenger of Allah (may Allah's peace and blessings be upon him). He started to recite, but the recitation became difficult for him. When he finished, he said: "Perhaps you recite behind your Imām?" We said: "Yes, that is so, O Messenger of Allah." He said: "Do not do so except with Sūrat al-Fātihah, since the prayer is invalid for the one who does not recite it."
Hasan/Sound. - [At-Tirmidhi]

Explanation

It was reported from ‘Ubādah ibn As-Sāmit that he said: "We were praying the dawn prayer behind the Messenger of Allah (may Allah's peace and blessings be upon him) and he started to recite but the recitation became difficult for him," i.e. he could not recite easily. So, when he finished he said: "Perhaps you recite behind your Imām?" The Companions (may Allah be pleased with him) answered: "Yes, O Messenger of Allah." It was as if the recitation became difficult for him and he did not know the cause so he asked them that question. This is indicated in his statement in another narration: "Why am I struggling with the Qur'an?" Most likely, the reason for the difficulty was the shortcoming which resulted from them deeming his recitation insufficient. One who enjoys perfection may be affected by the shortcomings of those behind him. The Sunnah directive for those praying behind the Imām is to recite silently, such that each person hears himself. And it is obligatory for the person praying alone as well as the Imām and those praying behind him to recite Sūrat al-Fātihah in both audible and silent prayers, given the soundness and specific indication of the relevant textual evidence. Then he directed them to adhere to reciting Sūrat al-Fātihah, saying: "Do not do so except with Sūrat al-Fātihah." It is probable that the forbiddance refers to reciting out loud, or reciting more than Sūrat al-Fātihah, so as not to distract or confuse the Imām and the worshipers praying behind him.