Hinduism believers can be anyone.

All believers to all believers. However, professionally, Imam or Sheihk

There is no standard collective noun for the noun 'believers'. However, there are collective nouns for the synonym 'worshipers', a congregation of worshipers, an assembly of worshipers, a gathering of worshipers.

If the 'believers' that you refer to are religious believers, the collective nouns for 'worshipers' will work well; a congregation of believers, an assembly of believers, or a gathering of believers.

because the lifestyle that nonbelievers live tempts believers to join in

believer or believers