"And when his eyes were opened, he saw nothing. And for three days he could not see." (Acts 9:9)
no means would he [Saul] have been able to see well again unless he had
first been fully blinded. Also, when he had rejected his own wisdom,
which was confusing him, he could commit himself totally to faith.
Since he had not believed that the Lord had conquered death by rising
on the third day, he was now taught by his own experience of the
replacement of three days of darkness by the return of the light.
Commentary on the Acts of the Apostles from the Venerable Bede