They are of the world: the pronoun, referring again to the false prophets, is emphatic and contrasts with the pronoun in “you are of God” in verse 4a.

Therefore, or ‘because of this fact,’ namely, that the false prophets are of the world.

What they say is of the world, in the Greek literally “out of the world they-speak”: structurally this clause parallels “you out of God you-are” (verse 4a) and “they out of the world they-are” (verse 5a). Semantically it further develops the latter clause by stating one of the main characteristics of those who “are of the world.”

Revised Standard Version‘s slightly adjusted rendering has the advantage of preserving the parallelism. The same may be true of such renderings as ‘they speak as the world speaks,’ ‘what they say has the quality of the world,’ ‘their teaching belongs to the world.’ But sometimes receptor language idiom requires renderings that neglect the parallelism or bring it out less fully; for example, ‘they speak the language of the world,’ ‘they talk about worldly things,’ ‘they talk about nothing but the world.’

The world listens to them: the verb may require a personal subject; for example, ‘the people of this world,’ ‘the friends (or party) of this world.’

The verb listens has the sense ‘to give attention to’; it signifies intentional, attentive hearing and may imply that the agent agrees to, or obeys, what is said, as is the case here. The rendering to be used here and in verse 6 is often a form of ‘to hear’ (as it is in the Greek). In some languages the verb does not take the speaking person as direct object but his words; hence ‘to listen to what they say.’

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 .