1 John 4:2

By this you know and recognize the Spirit of God: every spirit that acknowledges and confesses [the fact] that Jesus Christ has [actually] come in the flesh [as a man] is from God [God is its source];

1 Corinthians 12:3

Therefore I want you to know that no one speaking by the [power and influence of the] Spirit of God can say, “Jesus be cursed,” and no one can say, “Jesus is [my] Lord,” except by [the power and influence of] the Holy Spirit.

John 1:14

And the Word (Christ) became flesh, and lived among us; and we [actually] saw His glory, glory as belongs to the [One and] only begotten Son of the Father, [the Son who is truly unique, the only One of His kind, who is] full of grace and truth (absolutely free of deception).

John 16:13-15

But when He, the Spirit of Truth, comes, He will guide you into all the truth [full and complete truth]. For He will not speak on His own initiative, but He will speak whatever He hears [from the Father—the message regarding the Son], and He will disclose to you what is to come [in the future].

1 Timothy 3:16

And great, we confess, is the mystery [the hidden truth] of godliness:He (Jesus Christ) who was revealed in human flesh,
Was justified and vindicated in the Spirit,
Seen by angels,
Preached among the nations,
Believed on in the world,
Taken up in glory.

1 John 2:23

Whoever denies and repudiates the Son does not have the Father; the one who confesses and acknowledges the Son has the Father also.

1 John 4:3

and every spirit that does not confess Jesus [acknowledging that He has come in the flesh, but would deny any of the Son’s true nature] is not of God; this is the spirit of the antichrist, which you have heard is coming, and is now already in the world.

1 John 5:1

Everyone who believes [with a deep, abiding trust in the fact] that Jesus is the Christ (the Messiah, the Anointed) is born of God [that is, reborn from above—spiritually transformed, renewed, and set apart for His purpose], and everyone who loves the Father also loves the child born of Him.

Treasury of Scripture Knowledge

Summary

Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God:

General references

Bible References

Come

1 John 4:3
and every spirit that does not confess Jesus [acknowledging that He has come in the flesh, but would deny any of the Son’s true nature] is not of God; this is the spirit of the antichrist, which you have heard is coming, and is now already in the world.
John 1:14
And the Word (Christ) became flesh, and lived among us; and we [actually] saw His glory, glory as belongs to the [One and] only begotten Son of the Father, [the Son who is truly unique, the only One of His kind, who is] full of grace and truth (absolutely free of deception).
1 Timothy 3:16
And great, we confess, is the mystery [the hidden truth] of godliness:He (Jesus Christ) who was revealed in human flesh,
Was justified and vindicated in the Spirit,
Seen by angels,
Preached among the nations,
Believed on in the world,
Taken up in glory.

General references

Deuteronomy 18:21
If you say in your heart, ‘How will we know and recognize the word which the Lord has not spoken?’
John 8:47
Whoever is of God and belongs to Him hears [the truth of] God’s words; for this reason you do not hear them: because you are not of God and you are not in fellowship with Him.”