1 John 2:13

All three classes are first addressed in the present. "I write"; then in the past (aorist) tense, "I wrote" (not "I have written"; moreover, in the oldest manuscripts and versions, in the end of Jo1 2:13, it is past, "I wrote," not as English Version, "I write"). Two classes, "fathers" and "young men," are addressed with the same words each time (except that the address to the young men has an addition expressing the source and means of their victory); but the "little sons" and "little children" are differently addressed. have known--and do know: so the Greek perfect means. The "I wrote" refers not to a former Epistle, but to this Epistle. It was an idiom to put the past tense, regarding the time from the reader's point of view; when he should receive the Epistle the writing would be past. When he uses "I write," he speaks from his own point of view. him that is from the beginning--Christ: "that which was from the beginning." overcome--The fathers, appropriately to their age, are characterized by knowledge. The young men, appropriately to theirs, by activity in conflict. The fathers, too, have conquered; but now their active service is past, and they and the children alike are characterized by knowing (the fathers know Christ, "Him that was from the beginning"; the children know the Father). The first thing that the little children realize is that God is their Father; answering in the parallel clause to "little sons . . .

— Jamieson-Fausset-Brown Commentary (public domain)