Remember the only time that Scripture records that Jesus wrote something? It was when the adulterous woman was brought to him as a test.
They asked this to test him. They wanted to find a reason to bring charges against him. Jesus bent down and used his finger to write on the ground. When they persisted in asking him questions, he straightened up and said, “The person who is sinless should be the first to throw a stone at her.” Then he bent down again and continued writing on the ground. Jn 8.6-8 GW.
No one knows what he wrote, of course, since the text does not tell us.
But might Jeremiah 17.13 provide a tantalizing clue?
O Lord, the Hope of Israel, all who abandon you will be put to shame. Those who turn away from you will be written in dust, because they abandon the Lord, the fountain of life-giving water (GW).
The Hebrew text is a bit problematic, so that’s more reason not to be dogmatic.
Maybe, just maybe, the Lord was writing names in the dust, to “write off” his opponents. The idea in Jeremiah’s verse is judgment, where those who abandon the Lord will be destroyed.
Whatever Jesus was writing on the ground, we can be sure that, at that moment, it was nothing positive.