"The Blessed Paul who gathers us on this day has illuminated the earth. At the time he received his call, he was made blind; but his blindness made of him a torch for the world. He used to see to do evil; in his wisdom God made him blind so as to enlighten him for doing good. Not only did God reveal his power; he also revealed him the heart of the faith he was going to preach. He had to chase far away from him all the prejudices, close the eyes and lose the fake lights of reason to perceive the true doctrine, “become crazy to be wise” as he will say later on...Though one shouldn't believe that his call was imposed upon him; Paul was free to choose...
Fiery-natured, impetuous, Paul needed to be stopped abrubtly, to not be taken away by his ardor and despise the voice of God. Therefore God first repressed this fit of anger; by blinding him he calmed his anger; then he talked to him. He revealed him his ineffable wisdom, so that he could recognize the one who he used to fight and understand that he could not oppose himself anymore to his grace. It was not the lack of light that made him blind, but the overabundance of light.
God chose the right moment. Paul is the first to recognize it: “when (God), who from my mother's womb had set me apart and called me through his grace, was pleased he revealed his Son to me”...Let us then learn from the words of Paul himself, that neither he nor any other person have ever found Christ by their own personal spirit. It is Christ who reveals himself and who allows others to get to know him. As the Savior says: “It was not you who chose me, but I who chose you.”"
-Saint John Chrysostom