Hazrat Ubadah bin Samit narrates that the Holy Prophet (peace and blessings be upon him) led us in the Isha prayer, and during the prayer, he seemed to find the recitation burdensome. When he finished the prayer, he said, "Perhaps you were reciting behind your Imam?" We said, "Yes, O Messenger of Allah! We were doing so." The Holy Prophet (peace and blessings be upon him) said, "You should recite only Surah Al-Fatihah behind the Imam, because without it, the prayer is not valid."