The structure of the first sentence of this verse resembles that of 3.10. By this (see 2.3) points to the pair of opposite clauses in verses 2b and 3a. Some other renderings are ‘you can know the Spirit of God in this way:…’ (compare Goodspeed), ‘the test by which you can know the Spirit of God is this:….’

You know the Spirit of God is often better slightly expanded: ‘you can know/recognize the presence of the Spirit of God,’ ‘you can tell whether a person has (or is inspired by) the Spirit of God’; compare also Good News Translation‘s “you will be able to know whether it is God’s Spirit” (in which “it” refers to “the spirit they have” in verse 1).

The Greek verb form can also have the meaning of an imperative (compare Bible de Jérusalem), but the interpretation as an indicative is preferable for two reasons: (1) The verses state the standard for the test ordered in verse 1; such a statement is normally in the indicative. (2) In none of the other occurrences of this sentence structure is the introductory by this followed by a verb in the imperative.

Every spirit which confesses … is of God, or ‘every one who confesses … is inspired by God (or has the Spirit who comes from God)’ (compare Good News Translation), ‘if a person confesses…, the Spirit of God is in him.’

Confesses that Jesus Christ has come in the flesh: the Greek uses the participle of the perfect tense of “to come”; a more literal rendering would be “confesses Jesus Christ (as) having come in the flesh.” The use of the participle characterizes the utterance as a fixed formula. The perfect tense is to show that Christ’s coming in the past still influences the present. For a similar formula, but in another tense, and in the negative, see 2 John 7. For “to confess” see comments on 2.23.

Some versions take Christ with the participle; hence ‘confesses Jesus (as) Christ having come…,’ or, more freely, ‘confesses that Jesus is the Christ who has come…’ (compare Translators’ Translation and note). This rendering could be meant as a further clarification of 2.22. It is semantically attractive, but grammatically speaking the construction is less probable, since in the Greek it would normally require an article with the participial phrase.

In the flesh, or ‘as a human being’ (compare Good News Translation), “in human form” (Goodspeed); or, where ‘body’ has the connotation of what is only human, ‘taking his body here in the world,’ ‘with his very body.’ For the noun see comments on 2.16, meaning (4).

Quoted with permission from Haas, C., de Jonge, M. and Swellengrebel, J.L. A Handbook on The First Letter of John. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .