3 And by this we know that we have come to know him, if we keep his commandments. 4 Whoever says “I know him” but does not keep his commandments is a liar, and the truth is not in him, 5 but whoever keeps his word, in him truly the love of God is perfected. By this we may know that we are in him: 6 whoever says he abides in him ought to walk in the same way in which he walked.
(ESV)
5:1 Everyone who believes that Jesus is the Christ has been born of God, and everyone who loves the Father loves whoever has been born of him. 2 By this we know that we love the children of God, when we love God and obey his commandments. 3 For this is the love of God, that we keep his commandments. And his commandments are not burdensome. 4 For everyone who has been born of God overcomes the world. And this is the victory that has overcome the world—our faith. 5 Who is it that overcomes the world except the one who believes that Jesus is the Son of God?
(ESV)