John Calvin Commentary Acts 9:18

"And straightway there fell from his eyes as it were scales, and he received his sight; and he arose and was baptized;" — Acts 9:18 (ASV)

There fell from his eyes as it had been scales. The blindness of Paul, as we have said before, did not proceed from fear alone or from amazement; but by this means he was admonished of his former blindness, so that he might completely abandon that boldness and vain confidence with which he was puffed up.

He boasted that he was taught at the feet of Gamaliel (Acts 22:3), and undoubtedly he thought very well of his great intellect, which was, nevertheless, mere blindness. Therefore, he is deprived of his physical sight for three days, so that he may begin to see with his mind. For whoever seems wise to themselves must become fools, so that they may attain true wisdom.

For since Christ is the Sun of righteousness, in seeing without Him, we do not see; it is He also who opens the eyes of the mind. Both these things were shown to Paul, and in his person, they are shown to us. For he has his eyes covered with scales so that, condemning all his own knowledge as ignorance, he may learn that he has need of new light, which he had lacked until now. He is also taught that he must seek the true light from no one else but Christ, and that it is given by no other means except through His goodness.

Furthermore, while suffering from three days' hunger, he makes no haste to receive food until he is baptized. This shows the earnest desire he had to learn, because he did not refresh his body with food until his soul had received strength.