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 continues until all the accusers have left (John 8:9–10). The Bible is completely silent on what Jesus was carving into the dust. It's mentioned more than once, which suggests an important part of His response. He might have been writing Old Testament Scriptures which supported His point. Some have suggested He was 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.

Jesus proves that the mob who brought this woman is not trying to follow the Law in spirit, nor even in the letter. Under the Mosaic law, adulterers are subject to death by stoning (Leviticus 20:10; Deuteronomy 22:22). Yet the Law specifies both guilty persons are to be so punished. There is no guilty man present here (John 8:3–5)! 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). Jesus' challenge about the accusers' claims to morality results in a complete reversal. Every single one of the challengers leave (John 8:9).