The content is not indicated in any way. Only guesses can be made. An ancient tradition, starting with St. Jerome understands this as “the sins of the accusers.” The action of Jesus (“writing,” “drawing,” “registering”) is reported twice (Jn 8: 7-8). This interpretation suits the context of the gospel of John 8: 8 better but seems to be irrelevant in the context John 8: 7. Some speak of writing the statement of sentence before reading it according to the Roman legal custom. But how to explain the statement of Jesus in John 8: 11 if he has already written the statement of judgement earlier. A third opinion is based on Jeremiah 17: 13 – “… those who turn away from you shall be recorded in the earth,” for they have forsaken the fountain of living water, the Lord.” Further, a scholar conjectures that what Jesus could have written in the given time would be “you shall not join hands with a wicked man” (Ex 23: 16). Or perhaps in contrast to the tablets of stone written with ‘finger of God’ (cf. Ex 31: 18-19), is Jesus writing a new law of life with his finger…? But leaving all these possibilities, it is better to go for the simple probabilities that it was an action to spend time while the people around was challenged. Probably Jesus was simply drawing lines on the ground while thinking, containing the disgust for the wildly zealous Jews or expressing his imperturbability or calmness. As the evangelist has not given any indication, it is better to take it as not essentially important for the message.
When Jesus says to the woman, “Nor do I condemn you. You may go. But from now on, do not sin again,” it is clear that no compromise with sin is implied in the attitude of Jesus towards the woman. Compassion and understanding are not compromise and adjustment. Jesus understands the woman in her interior attitude of repentance but univocally demands a separation from her sinfulness.
In this narration John is creating a mock- Sanhedrin. The context is similar to a trial in the Sanhedrin. At the end of a trial the members of the Sanhedrin have to pronounce judgment one by one. In case of a complicated case, the judgment is stated starting from the eldest. The accused will be standing in front of the members. That is the position of the woman. When all left one by one starting from the eldest, it is tantamount to saying that all have pronounced her innocent.