Is performing the Night Vigil Prayer (Qiyam al-Layl) in congregation at the mosque after the Tarawih prayer considered an innovation (bid'ah)? Is it permissible to attend the congregational supplication (munajah) that takes place after every prayer and at the conclusion of the Qur'an recitation? Is it obligatory to remain in the mosque until the Imam finishes the supplication, or is it permissible to leave immediately after the prayer?

There is no harm in performing Tarawih prayers with twenty rak'ahs, more, or less. It is preferable for the worshippers to conclude with the Witr prayer, while ensuring tranquility in the prayer. Sheikh al-Islam Ibn Taymiyyah mentioned that the Prophet (peace be upon him) did not specify a particular number of rak'ahs for the night prayer in Ramadan (definition). The Companions would pray varying numbers according to their capacity; those who prolonged the prayer would reduce the number of rak'ahs, and those who shortened it, out of gentleness to the congregants, would increase the number of rak'ahs.

As for long, collective supplication (munajah): If it is at the point of Qunut in the last rak'ah of the Witr prayer, it is legislated. However, if it is after the prayer has concluded, it is an innovation (bid'ah) that was not practiced by the Companions or the Salaf. Those who do it should be admonished, and they should be taught the Sunnah (definition), which dictates that munajah, remembrance (dhikr (definition)), and supplication should be individual and in a low voice.

You must continue praying with them and invite them to the Sunnah, without following them in this collective supplication. Denounce with your hearts and tongues every action that deviates from the Sunnah. If they insist on performing this innovation and it is possible to pray in another mosque that adheres to the Sunnah, then that is preferable.

There is no specific supplication in the Prophetic Sunnah after completing the recitation of the Quran, nor from the Companions of the Prophet (peace be upon him) or the renowned Imams. Therefore, there is no basis for supplication after the ختمة (completion of Quranic recitation) within the prayer. However, outside of prayer, it has been authentically reported from Anas ibn Malik (may Allah be pleased with him), and there is no harm in it, provided it is not done collectively, persistently, or with adherence to a specific formula.