Who is a Christian

People ask me how to determine whether people are Christians or not. You can’t necessarily tell by watching them, because some non-Christians live outwardly moral lives, while some Christians sin in visible, public ways. You can’t tell by listening to them; if you listen long enough, the truth will probably come out, but some people guard their tongues very well. The way you can tell a person is truly a Christian is by what he desires. If he longs to praise and worship God and Christ, that is evidence of a transformed heart.

MacArthur, J. (2003). Hard to believe : The high cost and infinite value of following Jesus (167). Nashville, Tenn.: Thomas Nelson Publishers.