What is the ruling on gathering to supplicate on the Day of Arafah, whether in Arafat or elsewhere, where one person supplicates and the pilgrims repeat after him without saying "Ameen"? And is this action considered an innovation (bid'ah)?

The best for the pilgrim on the Day of Arafah is to strive in supplication and humility to Allah, raising his hands and facing the Qiblah, following the example of the Prophet (peace and blessings of Allah be upon him). Allah has legislated supplication with humility, privacy, and reverence, and this is one of the most excellent times for supplication. As for collective supplication, there is no basis for it, and it is safer to abandon it except for what has been authentically transmitted, such as Qunut prayer and prayers for rain. As for gathering for supplication in Arafah or elsewhere on this day, there is no basis for it.