1 John 1:10

He that believeth in the Son of God hath the witness in himself. 1st Because he hath in him the thing attested by God, namely this truth, that Christ is the Son of God.

2d. Because he hath in himself the very witness of God, and God Himself attesting.

3d. This testimony is the faith itself by which we believe the witness of God. There is a metonymy, because the object is put instead of the habit, or act tending to the object. It means, he who believes has a special gift of God, viz., faith. And this includes the witness, or testimony of God, and God Himself attests, which marvellously honours the believer, and makes him strong to confess Christ.

4th This testimony may be taken to signify the regeneration and adoption, the grace and glory of the believer meaning, He who believes in the Son of God hath in himself the witness of God, namely, that by which God witnesses to his soul and conscience by means of this faith with which he believes in Christ, that he is faithful, and a son and heir of God.

He that believeth not the Son, &c. As he that believeth in the Son, and receives God's testimony concerning Him, makes God to be true, and honours and worships Him; so, on the contrary, he that believeth not the Son, and rejects God's testimony concerning Him, makes God false, and does Him great despite.

Observe: instead of believe, the Greek has πεπίστευκεν, hath believed. This is a Hebraism by which the perfect is put for any tense.