2 Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God:
1 John 1
know . the Spirit of God-whether he be, or not, in those teachers professing to be moved by Him.
Every spirit-that is, Every teacher claiming inspiration by the Holy Spirit.
confesseth-The truth is taken for granted as established. Man is required to confess it, that is, in his teaching to profess it openly.
Jesus Christ is come in the flesh-a twofold truth confessed, that Jesus is the Christ, and that He is come (the Greek perfect tense implies not a mere past historical fact, as the aorist would, but also the present continuance of the fact and its blessed effects) in the flesh ("clothed with flesh": not with a mere seeming humanity, as the Docetæ afterwards taught: He therefore was, previously, something far above flesh). His flesh implies His death for us, for only by assuming flesh could He die (for as God He could not), Heb 2:9, 10, 14, 16; and His death implies His LOVE for us (Joh 15:13). To deny the reality of His flesh is to deny His love, and so cast away the root which produces all true love on the believer's part (1Jo 4:9-11, 19).
--Jamieson-Fausset-Brown Bible Commentary
From a compound of the base of G3674 and G3056; to assent, that is, covenant, acknowledge: - con- (pro-) fess, confession is made, give thanks, promise.
This word homologeo is a covenant word, from two words, homou--the same--and logos--mind of Christ. This 'confession' comes from the same mind [logos]
as Christ--homologeo--Jesus Christ is come in the flesh.
Come in the flesh, he thus is able to sanctify this tabernacle that we are currently living in.
1 Corinthians 1:30 It is because of him that you are in Christ Jesus, who has become for us wisdom from God--that is, our righteousness, holiness and redemption.