They were using this question as a trap, in order to have a basis for accusing him. But Jesus bent down and started to write on the ground with his finger.
“trap” = to put to the test with a view to failing. The whole point of their bringing the woman before Him was to catch Jesus, not to punish the woman. If He told them to stone her, He would be advising them to go against Roman law and rule and He would be inconsistent with what he had been teaching and saying, for He had welcomed sinners and harlots and said that He had come to seek and save the lost. If He told them to not stone her, He would be going against Jewish law. They thought they had Him trapped and there was no way out for Him.
“write” = to write or to draw. We don’t know what Jesus wrote or even if He was writing. There is an ancient tradition that Jesus wrote down sins of these accusers (compare Job 13:26). As Robertson points out, “That is not likely. They were written on their hearts.” What He did was show contempt for their accusations and methods by ignoring them and making them wait for His answer, which would give it greater effect. The sad fact is that, as Robertson notes, “Jesus alone on this occasion showed embarrassment over this woman’s sin.” His actions are a reminder of (Jer 17:13).
Job 13:26 For you write down bitter things against me and make me inherit the sins of my youth.
Jer 17:13 O LORD, the hope of Israel, all who forsake you will be put to shame. Those who turn away from you will be written in the dust because they have forsaken the LORD, the spring of living water.
This action of Jesus in not quickly answering His adversaries gives us an example to follow. When we are provoked, we should also be slow to respond. Some good advice is a take-off of the carpenter’s rule of measuring twice and cutting once — we should think twice and speak once.
It is interesting to note that this is not the first time God has written on the ground with His finger. The first recorded time was in (Ex 31:18).
Ex 31:18 When the LORD finished speaking to Moses on Mount Sinai, he gave him the two tablets of the Testimony, the tablets of stone inscribed by the finger of God.