The illustrious Sahaabi, ‘Abdullah bin Mas‘ood (radhiyallahu ‘anhu) was once invited to a waleemah function. When he was about to enter, he heard some impermissible activity taking place, hence he returned immediately. When he was questioned about the reason for his return, he explained: “I heard Rasulullah (sallallahu ‘alaihi wasallam) saying: ‘Whosoever adds to the numbers of a people, will be counted from among them, and the one who is pleased with the wrong of a people, will be a partner in their actions.’” (Ithaaful Khairatil Maharah vol. 4, pg. 135)
It is indeed extremely sad to notice many Muslims joining the disbelievers in their activities and festivities. There are those who remain as spectators and others actively participate. This hadeeth sounds a very severe warning for the passive participants, let alone those who actively join in the wrong.