Summary: Jesus did not condemn a woman caught in adultery, for himself to be condemned by God.
The teachers of the law and the Pharisees brought in a woman caught in adultery to Jesus, in order to have a basis for accusing him. They asked him, "Teacher, this woman was caught in adultery. In the Law Moses commanded us to stone such women. Now what do you say?"
Why did they bring this to Jesus? It’s becuase it was a dilemma to deal with such women. One the one hand, the Law regulates to stone such women (Deut. 22:22-24; Lev. 20:10). One the other hand, however, the Roman law did not sanction any death penalty by the Jewish self-government. Israelites were deprived by the Roman rulers of the right to excute death penalty, according to Josephus, 40 years before the destruction of Jerusalem(70 A.D.). That means, that already in the year of 30 A.D. they were deprived of the right to execute death penalty. So it was a dilemma to deal with such women. Not to stone her will directly violate the law of Moses. But obeying the law of Moses will automatically violate the Roman laws. Obeying the law of Moses would make Jesus be subjected to the Roman law. Rejecting the stoning would make him be despised by the Israelites.
At this, Jesus did not answer anything. He just bent down and started to write on the ground with his finger. I can not fully understand what this meant for the contemporaries. Maybe it was very strange to them, too. We know this because the teachers of the law and the Pharisees kept on questioning him, while he was writing something on the ground.
We can get a hint, however, from Roman court customs. At that time in the Roman court, it is said that the judges wrote the verdict before they sentenced it. If we read our story from the Roman background, Jesus’ writing on the ground might have meant that Jesus was writing a verdict on the ground on this case.
Some scholars conjecture, however, that Jesus’ writing is closely related to Jeremiah 17:23, where it says "O Lord, the hope of Israel, all who forsake you will be put to shame. Those who turn away from you will be written in the dust because they have forsaken the Lord, the spring of living water." Based upon the verse, some conjectures that Jesus was writing the names of accusers on the ground and by this performance Jesus meant a condemnation upon the accusers. It is a nice conjecture, but not sure.
Any way, the accusers kept on questioning Jesus. Then Jesus straightened up and said to them, "If any one of you is without sin, let him be the first to throw a stone at her." According to the law of Moses, it is the witnesses who should throw a stone first(Deut. 13:9; 17:7). Jesus just modified a word and meant any one without sin.
Surprise! Those who were accusing the woman began to go away one at a time, the older ones first, until only Jesus was left. They came with the confidence that the woman should be stoned. They came with the thought that the woman was a sinner and they were righteous. When they caught the woman from the adulterous scene, they were furious at her. However, when the word of Jesus was once uttered, they could now see their true identity. The light of Jesus shined upon their hearts and they could see their inner being. They thought they were right. But they were not! They were sinners, too. So they began to go away one at a time. They thought they were OK. They thought it was the woman only who should be stoned! But the light of Jesus was given to them and they could see their inner being. When they see the true Jesus and the true their identities, they could not stand there any more.