2 Corinthians 6:15 And what concord hath Christ with Belial? or what part hath he that believeth with an infidel?

An infidel is an unbeliever, a non-Christian, a pagan. The word “part” means “a part of a whole or portion”, more specifically, it describes “part of a whole that has been chosen or divided up share, portion.” In other words, the believer has no part in the lifestyle, practice, belief, allegiance of the unbeliever. The two simply cannot go together. They are totally no common ground of faith and practice.