Why did Paul have to suffer after his conversion?
After his conversion, Paul had to suffer because he had caused many of God's choice servants to suffer during his persecution. God's grace saved him, but he would still suffer for that persecution, and God also humbles those He uses, bringing them low rather than leaving them in high position.
Les teaches that Saul suddenly realized the one he was trying to stamp out was the same one he worshipped, and that revelation explains how he could endure everything afterward. God's grace saved him on the spot, but he was going to suffer for it because he had caused so many of God's choice servants to suffer during his persecution. The first thing God does is strike him blind. Saul asks, "Who art thou, Lord?" and the Lord answers, "I am Jesus whom thou persecutest." Les explains that it was hard for Saul to kick against the goads, like kicking into spikes: every time he persecuted, he ended up hurting. God showed him he was fighting a losing battle. Les also notes that God chooses the lowly; if a man begins in a high position, God takes him to the low spot, as with Moses, Egypt's second man, whom God could not use that way.