1 John 5:2

By this [ε ν τ ο υ τ ω]. Not by this or from this, as an inference (see on 4 6), but in the very exercise of the sentiment toward God, we perceive. When (grov). More strictly, whenever. Our perception of the existence of love to our brethren is developed on every occasion when we exercise love and obedience toward God.

Keep [τ η ρ ω μ ε ν]. Read poiwmen do. So Rev. See on John 3:21; 1 John 3:4. The exact phrase poiein tav ejntolav to do the commandments, occurs only here. See on Revelation 22:14.