Collective supplication after the prayer
Question: I have seen some worshippers, when they finish a congregational prayer, make supplication to Allah together and aloud after every prayer. Is this permissible? Kindly advise us and may you be rewarded.
Answer: Supplicating after the prayer is perfectly allowable, but each Muslim should do so on his own, beseeching Allah for himself, for his fellow Muslims, and for the good of his religion and worldly affairs. The supplication is to be made individually, not collectively.
As for gathering for a collective supplication after the prayer, that is a blameworthy innovation, because neither the Prophet ﷺ, nor his Companions, nor the righteous generations after them ever engaged in a practice where the imam would raise his hands, the congregation would raise theirs, and he would supplicate while they followed him in unison. This is an innovation.
However, if each person supplicates quietly to himself, without raising his voice or disturbing others, there is no harm in that—whether it be after an obligatory prayer or after a supererogatory one.
***
Praying two rak‘ahs before sleep
Question: I have a habit that I regularly maintain: I pray two rak‘ahs (units of prayer) before going to sleep, reciting al-Fāṭiḥah and a few short suras in them. Is this permissible, or is it an innovation?
Answer: What has been authentically reported from the Prophet ﷺ regarding etiquette before sleep is that a person should make ablution, lie down on his right side, recite Āyat al-Kursī (the Verse of the Throne) and the last two verses of Sūrat al-Baqarah, and say the various supplications transmitted from the Prophet ﷺ—there are many comprehensive ones. As for performing a specific prayer before sleep and holding fast to this practice, I know of no basis for it in the Prophetic Sunnah.