In John 7:53-8:11, the famous account of the woman caught in adultery, Jesus offers great insight into God's mercy and justice. John records the Lord's famous verdict (v. 7-11):
“Let him who is without sin among you be the first to throw a stone at her.” And once more he bent down and wrote on the ground. But when they heard it, they went away one by one, beginning with the older ones, and Jesus was left alone with the woman standing before him. Jesus stood up and said to her, “Woman, where are they? Has no one condemned you?” She said, “No one, Lord.” And Jesus said, “Neither do I condemn you; go, and from now on sin no more.”
Preaching from this passage in the fifth century, Augustine (Tractates on the Gospel of John 33.6-7) helpfully comments on this tension between mercy and holiness and how we tend to love the first but are slow to embrace the second:
"Neither will I condemn you." What is this, 0 Lord? Do you therefore favor sins? Not so, evidently. Mark what follows: "Go and sin no more." Therefore the Lord did also condemn, but condemned sins, not the sinner. For if he was a patron of sin, he would say, Neither will I condemn you; go, live as you will; be secure in my deliverance, however much you will to sin. I will deliver you from all punishment even of hell, and from the tormentors of the infernal world. He did not say this. Let them pay attention, then, who love his gentleness in the Lord, and let them fear his truth.... The Lord is gentle, the Lord is long suffering, the Lord is full of pity; but the Lord is also just, the Lord is also true. He bestows on you an interval for correction, but you love the delay of judgment more than the amendment of your ways (cited in Oden and Elowsky, On the Way to the Cross: 40 Days with the Church Fathers. Kindle Location 640-643).
Where do we need mercy and forgiveness today? In what area of our lives must we, by the Spirit's enabling power, go and sin no more?