By simple definition a Christian is a follower of Jesus The Christ—the Son of God who came in the flesh, died, and was resurrected. The Bible speaks extensively about the subsequent lifestyle of believers—what it calls fruit. For example, we read about “the fruit of the Spirit”:

But the fruit of the Spirit is love, joy, peace, longsuffering, kindness, goodness, faithfulness, gentleness, self-control. Against such there is no law. And those who are Christ’s have crucified the flesh with its passions and desires. (Galatians 5:22–24, emphasis mine)

This wholesome fruit stands in contrast to “the unfruitful works of darkness”:

Therefore be imitators of God as dear children. And walk in love, as Christ also has loved us and given Himself for us, an offering and a sacrifice to God for a sweet-smelling aroma. But fornication and all uncleanness or covetousness, let it not even be named among you…