9:17 Ananias departed, and entered into the house. 
Laying his hands on him, he said, "Brother Saul, the Lord, 
who appeared to you on the road by which you came, has sent me,
that you may receive your sight, and be filled with the Holy Spirit." 
9:18 Immediately something like scales fell from his eyes, and he received his sight. 
He arose and was baptized. 
9:19 He took food and was strengthened.

Saul stayed several days with the disciples who were at Damascus. 
9:20 Immediately in the synagogues he proclaimed the Christ, that he is the Son of God. 
9:21 All who heard him were amazed, and said,
"Isn't this he who in Jerusalem made havoc of those who called on this name? 
And he had come here intending to bring them bound before the chief priests!" 
9:22 But Saul increased more in strength, 
and confounded the Jews who lived at Damascus, proving that this is the Christ. 
 

In view of the fact that Paul gained the position of Apostle not through faith nor any virtue of his own tells us that such a role is not born of reward but of responsibility. We saw in the case of Judas that such a role of responsibility incurs greater judgment in the end. But that possessing such a role does not guarantee that one will be saved. Paul was to be the replacement of Judas. A persecutor replaced a betrayer. Yet as an apostle Paul was to turn out much different than Judas. People are often too proud and presumptuous of their own opinions as to how they think things will turn out in the end. I wonder if God throws in surprises in life like these just to frustrate such people.

Paul was the least likely candidate to be an apostle to the Gentiles. He had not believed in Jesus during his earthly ministry despite the miracles and not only disbelieved Christians like Stephen who presented the gospel to him, but even persecuted them to the death. Furthermore he was of the religious elite of whom Jesus denounced for their hypocrisy. He certainly was not empathic towards Gentiles but was no doubt more xenophobic than the other apostles, being particularly zealous for the Law of Moses. We would think he would have turned out to be the most legalistic of the apostles. But he turned out quite differently. Paul's conversion and resultant ministry is another miraculous evidence affirming the gospel. For there is no other reasonable explanation for the transformation of this man.

It is insightful to consider also Paul's view on his being chosen:

"I became a servant of this gospel by the gift of God’s grace given me through the working of his power.  Although I am less than the least of all God’s people, this grace was given me: to preach to the Gentiles the unsearchable riches of Christ, and to make plain to everyone the administration of this mystery" Eph 3:7-9

"I am the least of the apostles and do not even deserve to be called an apostle, because I persecuted the church of God.  But by the grace of God I am what I am, and his grace to me was not without effect. No, I worked harder than all of them— yet not I, but the grace of God that was with me." 1Cor 15:9,10

"I thank Christ Jesus our Lord, who has given me strength, that he considered me faithful, appointing me to his service.  Even though I was once a blasphemer and a persecutor and a violent man, I was shown mercy because I acted in ignorance and unbelief." ITim 1:12,13

Then he seemingly excuses himself saying that it was because of his ignorance and unbelief that he was shown mercy. But then again aren't all sins committed with an element of ignorance and unbelief? Apparently not to the same degree. For some sins are done knowingly and willfully and there are those done blindly. This is not to excuse those done blindly. Yes, they are also subject to judgment, but to a lesser degree. 

"If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left,  but only a fearful expectation of judgment and of raging fire that will consume the enemies of God." Heb 10:26,27 And "If they have escaped the corruption of the world by knowing our Lord and Savior Jesus Christ and are again entangled in it and overcome, they are worse off at the end than they were at the beginning." 2Peter 2:20

But why would God chose an elite Pharisee, an arrogant and violent man? It seems to me such a man would be despised by the Christians. After all, he was a Pharisee. Such a word was and is not particularly honorable in the Christian community. After he became a Christian he faced a great deal of hostility both from the Jews and even from Christians who were suspicious of him. He was to be more humiliated than the other apostles. For they could speak freely in Jerusalem and they enjoyed popularity among the Christians there. But if Paul preached there he would be threatened with death. He was sent to the Gentiles, which to the other Apostles is like garbage duty. It was too humilating for them to preach to such dogs. They wouldn't even eat with the Gentiles. But Paul would become as if one of them. Though facing so much humiliation in his ministry, it could be argued today that he became the most important man in history second to Jesus. His writings have been the most read of all time. And like Jesus he became another example of God exalting the humble. So if you want to be greatly used by God, be prepared to face humiliation.