Again a new commandment (παλιν εντολην καινην). Paradox, but truth. Old in teaching (as old as the story of Cain and Abel, 3:11f.), but new in practice. For this use of παλιν for a new turn see John 16:28. To walk as Christ walked is to put in practice the old commandment and so make it new (ever new and fresh), as love is as old as man and fresh in every new experience.

True in him and in you (αληθες εν αυτω κα εν υμιν). This newness is shown supremely in Christ and in disciples when they walk as Jesus did (verse 1. John 2:6).

Because (οτ). Explanation of the paradox.

Is passing away (παραγετα). Present middle indicative of παραγω, old verb, to lead by, to go by (intransitive), as in Matthew 20:30. Night does pass by even if slowly. See this verb in verse 1 John 2:17 of the world passing by like a procession.

True (αληθινον). Genuine, reliable, no false flicker.

Already shineth (ηδη φαινε). Linear present active, "is already shining" and the darkness is already passing by. Dawn is here. Is John thinking of the second coming of Christ or of the victory of truth over error, of light over darkness (cf. John 1:5-9), the slow but sure victory of Christ over Satan as shown in the Apocalypse? See 1 John 1:5.