The eighteenth-century pastor and theologian Jonathan Edwards wrestled with this text and concluded, “Saving faith implies . . . love. . . . Our love to God enables us to overcome the difficulties that attend keeping God’s commands — which shows that love is the main thing in saving faith, the life and power of it, by which it produces great effects.”
I think Edwards is right and that numerous texts in the Bible support what he says.
Another way to say it is that faith in Christ is not just assenting to what God is for us, but also embracing all that he is for us in Christ. “True faith embraces Christ in whatever ways the Scriptures hold him out to poor sinners.” This “embracing” is one kind of love to Christ — that kind that treasures him above all things.
Therefore, there is no contradiction between 1 John 5:3, on the one hand, which says that our love for God enables us to keep his commandments, and verse 4, on the other hand, which says that our faith overcomes the obstacles of the world that keep us from obeying God’s commandments. Love for God and Christ is implicit in faith.
Verse 5 defines the faith that obeys as “the one who believes that Jesus is the Son of God.” This faith is “embracing” the present Jesus Christ as the glorious divine person he is. It is not simply assenting to the truth that Jesus is the Son of God, because the demons assent to that (Matthew 8:29). Believing that Jesus is the Son of God means “embracing” the significance of that truth — that is, being satisfied with Christ as the Son of God and all God is for us in him.
“Son of God” means that Jesus is the greatest person in the universe alongside his Father. Therefore, all he taught is true, and all he promised will stand firm, and all his soul-satisfying greatness will never change.
Believing that he is the Son of God, therefore, includes banking on all this, and being satisfied with it.