26 Saul, Saul, why do you persecute me? He who had conquered His persecutors in the world below, and ruled over the angels in the world above, spoke from above with humble voice. And He Who while He was upon earth had denounced ten woes against His crucifiers, when He was in heaven, did not denounce even one woe against Saul, His persecutor. Now, our Lord denounced woe to His crucifiers, that He might teach His disciples not to be dismayed by His murderers.
But our Lord spoke in humility from heaven, that in humility the heads of His church might speak. And if any one should say, “Wherein did our Lord speak humbly with Paul? For lo! The eyes of Paul were grievously smitten;” let him know that it was not from our merciful Lord that this chastisement proceeded, who spoke those words in humility; but from the vehement light that vehemently shone forth there. And this light did not strike Paul by way of retribution on account of his deeds, but on account of the vehemence of its rays it hurt him, as he also said: When I arose, I could discern nothing for the glory of the light. But if that light was glorious, O Paul, how did the glorious light become a blinding light to you yourself?
The light was that which, according to its nature, illuminates above, but contrary to its nature, it shone forth below. When it illumined above, it was delightful; but when it shone forth below, it was blinding. For the light was both grievous and pleasant. It was grievous and violent towards the eyes of the flesh; and it was pleasant and lightful to those who are fire and spirit.
Source: On Our Lord (New Advent)