“The doctrine of love can be used by Christians to test themselves to see whether their Christian experience is real. If it is, they will have love inside them, welling up within them, and flowing out of them. True light emits heat.
When the truth of the gospel is discovered, the heart of love begins to boil excitedly within the soul. People in this condition direct their love towards God as the supreme good. In love they unite their hearts to Christ, and they focus their heart on flowing love towards God’s people. Indeed, they seek to love all people.
This is just what happens when people genuinely discover that Christ is all we need and that he is excellent beyond comparison. People who believe the true gospel correctly will always accompany their belief with love.
Oh, how people love the one they believe to be the Christ, the Son of the living God! The truths of the gospel become like ropes that grab the heart and pull it closer to God in Christ. Each gospel teaching is like a rope and together they form many ropes, all holding tightly to the person’s heart, drawing it closer and closer to God in love. When people have a genuine experience of trusting and relying on Christ, love pulls them towards him. They rely upon him with delight and true joy in their hearts, gladly and sincerely submitting their souls to his loving care.
In the Song of Solomon 2:3, the wife was placed beneath Christ’s shadow. She sat there with great delight, resting under the sweet shade of his protection. She did this because she loved him. This is how all those who trust in Christ should feel, for when people go through the delightful experience of true comfort and spiritual joy, they respond with a heart of love. Likewise, this kind of comforting, spiritual joy is the result of true faith and true love. However, it’s not that they rejoice in themselves, rather, God supplies their overwhelming joy.
In the same way, when people come to experience true hope, it invariably brings with it a heartfelt love for God, and there will certainly be evidence of this. Indeed, true hope fills up the heart with love, and it does not bring shame to the person who has it:
Romans 5:5 Hope does not put us to shame, because God’s love has been poured into our hearts through the Holy Spirit who has been given to us.
In all of these ways, the doctrine of love provides a forum for people to test their own hearts, to see if they are truly in Christ. If they are, the spiritual joy and true hope Christ brings will overflow the heart with love.”
– From Jonathan Edwards’ sermon, Love the Sum of All Virtue (updated for today’s readers). The entire updated message is available as a bonus sermon in Sinners in the Hands of an Angry God: Updated to Modern English.