What does John 8:8 mean?

This is the second time in a few short verses where Jesus is said to have written on the ground (John 8:6). In fact, He apparently does not stop writing until after all of the accusers have left (John 8:9–10)! The Bible is completely silent on exactly what Jesus was carving into the dust. The fact that it's mentioned more than once suggests that it's an important part of His response. He might have been writing Old Testament Scriptures which supported His point. Or, as some have suggested, He may have been recording the names and sins of some of the woman's accusers. One can assume that whatever He wrote was at least part of the reason the Pharisees and Scribes abandon their attempt.

In general, Jesus reacts by proving that the mob who has brought this woman is not actually trying to follow the law, either in spirit or even in the letter. Adulterers are subject to death by stoning (Leviticus 20:10; Deuteronomy 22:22), but the law specifies both guilty persons are to be so punished. There is no guilty man present here! Further, the law says that those who make the accusation are to begin the execution themselves (Deuteronomy 17:7). The Old Testament demands right judgment and mercy as much as it does holiness (Proverbs 21:10; Zechariah 7:8–9; Matthew 23:23). This, combined with Jesus' challenge about the accusers' claims to morality, results in a complete reversal. Every single one of the challengers leave (John 8:9).