“This they said, tempting him, that they might have to accuse him. But Jesus stooped down, and with his finger wrote on the ground, as though he heard them not.”
This they said, tempting him, that they might have to accuse him. But Jesus stooped down, and with his finger wrote on the ground, as though he heard them not — John explicitly identifies the authorities' motive: they are 'tempting' (peirazō, testing) him to trap him into saying something accusable. Jesus's response is enigmatic: he 'stooped down' (katakúpsas) and wrote on the ground with his finger. The writing is mysterious; John does not say what he wrote. His apparent inattention ('as though he heard them not') defuses the trap by refusing to engage on the authorities' terms. The gesture may evoke Exodus 31:18 (God writing the Law with his finger) or Daniel 5:5 (writing judgment), suggesting Jesus's transcendent role.
Church Fathers on John 8:6
Our Lord at the time of His passion used to spend the day in Jerusalem, preaching in the temple, and performing miracles, and return in the evening to Bethany, where He lodged with the sisters of Lazarus. Thus on the last day of the feast, having, according to His wont, preached the whole day in the temple, in the evening He went to the mount of Olives.
And where ought Christ to teach, except on the mount of Olives; on the mount of ointment, on the mount of chrism. For the name Christ is from chrism, chrism being the Greek word for unction. He has anointed us, for wrestling with the devil.
And next it is signified, that after He began to dwell by grace in His temple, i.e. in the Church, men from all nations would believe in Him: And all the people came to Him, and He sat down and taught them.