We know that …: the Greek expresses we both by the verbal ending and the pronoun. This is to emphasize the contrast between we (namely, those who know that they “have passed out of death into life”) and the world (which remains in death).

We have passed out of death into life: the perfect tense of the verb serves to show that the reference is to an enduring situation viewed as the result of an event in the past. The verb refers to movement from one place or situation to another. Because it is combined with two contrasting prepositions, it is sometimes better translated by two verbs; for example, ‘to leave,’ ‘to go away from,’ and ‘to enter,’ ‘to go (in)to,’ ‘to arrive at.’ See also the two alternative renderings to be mentioned below.

The nouns death and life may have to be rendered by terms from another word class. The former noun is used here in a metaphorical sense to refer to an existence in the sphere and under the power of death and outside the domain of God. Its meaning parallels that of “darkness” in 1.5. Life (see comments on 1.1) is the opposite of death in all the points mentioned. These and other considerations may result in renderings of the clause such as ‘we have stopped being dead and started being alive,’ ‘we are no longer dead but begin to live (now).’

One has to seek a term in the receptor language that refers to death in a clear and plain way without being offensive. If the common word cannot be used in the required metaphorical sense, one will have to shift to a simile; for example, ‘we are no longer like one dead.’

Because we love the brethren gives the reason, or the proof, of “we know.” One must avoid a rendering in which the clause can be taken as the cause or reason of the directly preceding “we have passed … into life.” Therefore some translators have repeated the verb ‘to know,’ inserting ‘we know it/this’ before ‘because we love…’ (compare Good News Translation and several others), or have shifted the latter clause to the head of the sentence; compare, for example, ‘because we love the brothers, we know that we have passed … into life.’ For yet another solution, compare “we for our part have crossed over from death to life; this we know, because we love our brothers” (New English Bible).

The plural the brethren, or “the brothers,” ‘our brothers,’ is used here (and in verse 16) to show that the reference is to individual persons, whereas the singular is used when the reference is to the group viewed collectively (compare 2.9-11; 3.10, 15, 17; 4.20-21; 5.16).

He who does not love: the verb love is without a goal, probably to suggest an unlimited application. If, however, the corresponding receptor language expression cannot be construed without a goal, one may add ‘his brother’ (as some Greek manuscripts do also), or perhaps ‘the/his brothers.’

Remains in death, or ‘is still in (the power/domain of) death,’ ‘is and remains ruled by death,’ ‘is and continues to be (like a) dead (person),’ ‘is (like) dead now and forever.’ The present tense emphasizes the idea of continuing reality. Compare also comments on “to abide” in 2.10.

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 .