John Calvin taught through the doctrine of “Limited Atonement” that a person has no power to resist because what God does is change an unwilling heart to a willing heart. Calvin used Ezekiel 11:19: “And I will give them one heart, and I will put a new spirit within you; and I will take the stony heart out of their flesh, and will give them an heart of flesh.” Calvin taught that faith is given to the elect sinner by God through a direct operation of the Holy Spirit above and apart from the word. Furthermore, the Spirit never fails to bring the elect to conversion.
Consider for a moment, though, that the gospel is the power of God unto salvation (Romans 1:16; 1 Corinthians 15:1-2). In Acts 8, what caused the Samaritans to believe was that they heard what Philip said and saw the miracles he performed. There was no mention of the Spirit’s coming upon them until after they had obeyed the gospel (Acts 8:17). With Saul of Tarsus (Acts 9; 22; 26), there was no direct operation upon his heart. What happened was that genuine evidence was presented to him that he could not ignore.
There is no evidence at all that God sent a “first work of grace” upon Saul. In Acts 10-11, an angel appeared to Cornelius. The angel did not perform an operation upon Cornelius’ heart. He told him to fetch Peter who would come and tell him words whereby he would be saved (Acts 11:14). The law of the Spirit makes free (Romans 8:2). The law is the rule of action; the Spirit is not law but the Spirit converts through the law; it is perfect, converting the soul (Psalm 19:9).