Matthew Poole and continuators on 1 John 4:2

2 Hereby know ye the Spirit of God; Every spirit that confesseth that Jesus Christ is come in the flesh, is of God.

He here gives them the general Rule, both affirmative and negative, which would suffice them to judg by in their present Case. This being the great Controversy of that Time with the Iews, Whether Iesus were the Messiah? and whether the Messiah were as yet come or no? And with the Gnosticks, Whether he were really come in the Flesh, in true humane Nature? or were not, as to that appearance; a meer Phantasm? And he affirms, They that confest him so come, were of God; i. e. thus far they were in the right, this Truth was of God. Of the two litigating Parties, this was of God, the other not of God; this took his Side, that was against him. Yea, and they that not only made this true Confession, but did also truly confess him, i. e. sincerely, cordially, practically, so as accordingly to trust in him, subject and devote themselves to him, were born of God, his very Children, acted and influenced hereunto by his own holy Spirit, as chap. 5.1, 5. Mat. 16.16, 17. 1 Cor. 12.3.