1 John 4:2-3

2 Here's how you test for the genuine Spirit of God. Everyone who confesses openly his faith in Jesus Christ - the Son of God, who came as an actual flesh-and-blood person - comes from God and belongs to God.

3 And everyone who refuses to confess faith in Jesus has nothing in common with God. This is the spirit of antichrist that you heard was coming. Well, here it is, sooner than we thought!