The scribes and the Pharisees brought a woman who had been caught in adultery, and placing her in the midst they said to him, "Teacher, this woman has been caught in the act of adultery. Now in the Law Moses commanded us to stone such. What do you say about her?" This they said to test him, that they might have some charge to bring against him. Jesus bent down and wrote with his finger on the ground. And as they continued to ask him, he stood up and said to them, "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 with his finger on the ground. But when they heard it, they went away, one by one, beginning with the eldest, and Jesus was left alone with the woman standing before him. Jesus looked 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 do not sin again." John 8:3–11 (RSV)
Those who are seeking to destroy another human being will use whatever tool that presents itself. The scribes and the Pharisees wanted to discredit Jesus in as public a manner as possible. The Law of Moses allowed for adulterers to be stoned to death. (Leviticus 20.10) The Law allowed for it, but it was not consistently practiced in Jesus' day. The proof of this is shown by who is brought to Jesus. Adultery takes at least two people, and only one, the woman, was presented for punishment. The man involved probably got a lecture and sent on his way.
The woman was guilty of adultery. She did not protest her innocence, nor did anyone speak on her behalf. The scribes and the Pharisees had the legal right to stone her to death. No guilt would be laid on them for the Law justified their actions. Again, they thought they had Jesus. If he let her go, they could say He rejects the Law of Moses. If He allowed her to be stoned, it would make of mockery of Jesus' teaching about the love and mercy of God.
They also made sure that a large crowd gathered to administer 'justice'. After all, who doesn't like a good stoning? Punishing someone else's sin takes the burden off of you, shifting it to the poor soul who had the bad taste to get caught.
Jesus measures His time in responding. Who knows what He wrote in the dust as the mob was getting ready to act. When you are eager for something to happen, time seems to slow down. Those who had brought their stones, keen to use them, must have thought, 'what is He waiting for? It is a clear cut case of adultery.' They kept asking Him to say something, give the signal to begin.
The mob tensed as one person when Jesus stood up to speak: "Let him who is without sin among you be the first to throw a stone at her." He knelt again and wrote. His words must have been like an electric shock running through the mob. They stood frozen as Jesus' words sank in.
They glanced side to side, not daring to look anyone in the face. No one was so arrogant as even to consider casting the first stone. Jesus confronted them with their sin. No one could pretend he had not sinned. The older men left first as age is a good teacher of the truth about ourselves. It wasn't long before it was Jesus and the woman left. 'Who is there to accuse you now?' He asked. Where only minutes before there were bloodthirsty people ready to stone her, only Jesus remained.
'No one is left.' She said. Jesus did not condemn her either, though He alone had the right to do so. He offered mercy to her, mercy she did not deserve. He also admonished her, 'Go, and sin no more." Jesus does not pretend that sin is a small matter. He doesn't tell the woman, 'next time, don't get caught.' No, He tells her to become a new person, a person devoted to God.
Jesus shows the same mercy to each of us when our sins are forgiven. He forgives us day by day, for we sin daily. Were it not for Jesus; we would die in our sin. We, like the woman, are given mercy and a command to leave sin behind us.