1Jn 4, 2 How you can know the Spirit of God

(1Jn 4, 2) How you can know the Spirit of God
[2] This is how you can know the Spirit of God: every spirit that acknowledges Jesus Christ come in the flesh belongs to God,

(CCC 463) Belief in the true Incarnation of the Son of God is the distinctive sign of Christian faith: "By this you know the Spirit of God: every spirit which confesses that Jesus Christ has come in the flesh is of God" (1 Jn 4:2). Such is the joyous conviction of the Church from her beginning whenever she sings "the mystery of our religion": "He was manifested in the flesh" (1 Tim 3:16). (CCC 465) The first heresies denied not so much Christ's divinity as his true humanity (Gnostic Docetism). From apostolic times the Christian faith has insisted on the true incarnation of God's Son "come in the flesh". (Cf. 1 Jn 4:2-3; 2 Jn 7). But already in the third century, the Church in a council at Antioch had to affirm against Paul of Samosata that Jesus Christ is Son of God by nature and not by adoption. The first ecumenical council of Nicaea in 325 confessed in its Creed that the Son of God is "begotten, not made, of the same substance (homoousios) as the Father", and condemned Arius, who had affirmed that the Son of God "came to be from things that were not" and that he was "from another substance" than that of the Father. (Council of Nicaea I (325): DS 130, 126). (CCC 480) Jesus Christ is true God and true man, in the unity of his divine person; for this reason he is the one and only mediator between God and men. (CCC 483) The Incarnation is therefore the mystery of the wonderful union of the divine and human natures in the one person of the Word.