What does John 8:6 mean?

During Jesus' public ministry, He was often challenged by critics such as the Pharisees and Sadducees. Their questions were rarely sincere. Most were overt attempts to trick Jesus and discredit Him (Matthew 16:1; 19:3; 22:35; Luke 10:25; 11:53–54). These attempts never succeeded. In fact, they often wound up embarrassing the critics! Here, the Pharisees attempt to use a more dramatic approach: a real-life moral dilemma. The woman they have brought is unquestionably guilty (John 8:4); neither is there a question about the law which prescribes death for adulterers (Deuteronomy 22:22; Leviticus 20:10). Their hope is that Jesus will either stone her, ruining His merciful reputation (Matthew 11:19; Luke 6:36) and breaking Roman law (John 18:31), or He will refuse and prove that He does not honor the law of Moses.

Jesus does not take the bait. He says nothing at first. Instead, He begins to write on the ground. This puzzling detail is one of the New Testament's richest sources of speculation. The Bible gives not even a clue as to what Christ is writing. Perhaps He is writing the exact Old Testament quotations these men cite to Him. Maybe He is writing the names of the critics, alongside their own sins, in preparation for His surprising response (John 2:24–25). Jesus may even have been writing a question such as "where is the man who was also caught in the act?" Given how quickly Jesus' critics will abandon their attack, and the prominence it is given in the story, His writing probably factored heavily into their reaction.

While we don't know what Jesus wrote, we do see how He turns the hypocrisy of these Pharisees against them. They were not wrong to seek justice under the Law. However, they are clearly not following it fully; they have only brought half of the guilty ones. Also, God's law prioritized mercy over blind punishment (Proverbs 21:10; Zechariah 7:8–9; Matthew 23:23).