By their fruit.

22 But the fruit of the Spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness, 23 gentleness and self-control. Against such things there is no law. 24 Those who belong to Christ Jesus have crucified the flesh with its passions and desires. 25 Since we live by the Spirit, let us keep in step with the Spirit. 26 Let us not become conceited, provoking and envying each other. (Galatians 5:22-26)