Verses 7-9 give the reason for the preceding exhortation: only by keeping the command to love will the Christians be able to hold their own against the false teachers, whose denial of the Incarnation implies that they did not practice the love Jesus preached.
Many deceivers have gone out into the world: this clause closely resembles 1 John 4.1c (which see), except for two differences: for deceivers the other verse has “false prophets”; instead of the aorist tense of the Greek verb the other verse uses the perfect tense. If the latter difference is intentional, it is to indicate that here the process is viewed simply as a past act, but in 1 John 4.1 as a past act with results continuing in the present.
Deceivers: the Greek word used here is an agent noun referring to persons who are habitually deceiving people. It differs from “those who would deceive” (1 John 2.26, which see) in that it does not express an attempt. For “the world” see comments on 1 John 2.15, meaning (2).
Men who will not acknowledge the coming of Jesus Christ in the flesh is an appositional phrase going with deceivers but may better be rendered as a full sentence; for example, ‘They (are men who) will not acknowledge the coming….’ What is stated in this clause forms the negative counterpart of what is said in 1 John 4.2b, which see.
Men who will not acknowledge: the Greek uses a present tense form. Therefore one can better say “men who do not acknowledge” (New English Bible, compare also Good News Translation, Translators’ Translation). For the verb see comments on “to confess” in 1 John 2.23.
The coming of Jesus Christ in the flesh can be restated as ‘that Jesus Christ comes in the flesh.’ The Greek uses a participle of the present tense, which characterizes the phrase as a fixed formula stating the fact of the Incarnation. The receptor language may require a past tense form; for example, ‘that Jesus Christ came (or has come) in the flesh.’
To take the verb form as a reference to Christ’s continuous coming gives no satisfactory sense. To take it as having future force and the clause as referring to Jesus’ second advent is grammatically possible but is highly improbable in this context.
Such a one is the deceiver and the antichrist: this clause gives a similar view on the relationship between the false teachers and the antichrist as found in 1 John 4.3, but it is phrased differently.
Such a one is, in the Greek literally “this-one,” is pointing backward to men who will …. It may have to be adjusted in order to bring out the meaning more clearly or to ease the shift from the plural (men) to the singular; for example, ‘whoever is like these persons is,’ ‘it is in a person resembling these men that we see.’ Or one may say “that is the mark of,” following Goodspeed, who shifts from the persons to the situation those persons are in.
The deceiver and the antichrist forms the predicate of the sentence. The two nouns refer to one and the same person, and they are closely connected. The definite articles serve to indicate that the designations were well known to the readers. The nouns tend to function as titles, the second probably still more so than the first.
Where the terms might be misunderstood as referring to different persons, it may be better to omit the connective; for example, ‘the Deceiver, the Antichrist’ (compare Bible de Jérusalem). Semantically speaking the first term qualifies the second. To bring this out one may change the word order; compare “the Antichrist, the archdeceiver” (New English Bible), or, where necessary, shift to a relative clause, ‘the antichrist who is a deceiver (or is always deceiving).’ For “antichrist” see comments on 1 John 2.18.
Quoted with permission from Haas, C., de Jonge, M. and Swellengrebel, J.L. A Handbook on The Second Letter of John. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .