What is the ruling on communal remembrance (dhikr) aloud, and specifying a particular formula for individual remembrance, and repeating the formula of remembrance aloud while others are silent?

Collective dhikr in a single voice is impermissible. However, if one person instructs others to recite a specific dhikr and they repeat it, or if he recites it along with them, there is no harm if it is for a valid purpose like teaching. But if it is solely for the purpose of worship, it is impermissible because it was not transmitted from the Prophet (peace be upon him) or his Companions, and the fundamental principle regarding acts of worship is adherence to what is prescribed and imitation. Ibn Mas'ud (may Allah be pleased with him) condemned those who engaged in this, as it is a mannerism not practiced by the Companions, and he said: "Follow and do not innovate, for you have been sufficed, and every innovation is misguidance." Hudhayfah (may Allah be pleased with him) said: "Follow our path, for if you follow us, you have indeed preceded far; and if you oppose us, you have indeed gone far astray."