1 John 3:19-20
The “this” that he talks about is Love, and how we know what Love is. So, rephrased: “Love is how we know we belong to the truth.” Love truly is, all we need.
I also like how John says (at the end), “and he knows everything”. As if to says, “no duh! You forgot again.. I’ll just keep telling you I guess”.
God. Is. Greater.