One who heard us was a woman named Lydia, from the city of Thyatira, a seller of purple goods, who was a worshiper of God. The Lord opened her heart to pay attention to what was said by Paul. (Acts 16:14)
Everywhere Paul preached some believed and some did not. How are we to understand why some of those who are dead in trespasses and sins (Ephesians 2:1, 5) believed and some did not?
The answer why some did not believe is that they “thrust it aside” (Acts 13:46) because the message of the gospel was “folly to [them], and [they were] not able to understand” (1 Corinthians 2:14). The mind of the flesh “is hostile to God, for it does not submit to God’s law; indeed, it cannot” (Romans 8:7).
Everyone who hears and rejects the gospel “hates the light and does not come to the light, lest his works should be exposed” (John 3:20). They remain “darkened in their understanding . . . because of the ignorance that is in them, due to their hardness of heart” (Ephesians 4:18). It is a guilty ignorance. The truth is available. But “by their unrighteousness [they] suppress the truth” (Romans 1:18).
But why then do some believe, since all are in this condition of rebellious hardness of heart, dead in their trespasses? The book of Acts gives the answer in at least three different ways. One is that they are appointed to believe. When Paul preached in Antioch of Pisidia, the Gentiles rejoiced and “as many as were appointed to eternal life believed” (Acts 13:48).
Another way of answering why some believe is that God granted repentance. When the saints in Jerusalem heard that Gentiles, and not just Jews, were responding to the gospel, they said, “Then to the Gentiles also God has granted repentance that leads to life” (Acts 11:18).
But the clearest answer in Acts to the question why a person believes the gospel is that God opens the heart. Lydia is the best example. Why did she believe? Acts 16:14 says, “The Lord opened her heart to pay attention to what was said by Paul.”
If you are a believer in Jesus, all of these happened to you: You were appointed to believe; you were granted to repent; and the Lord opened your heart. The rest of your life you should be overflowing with amazed thankfulness at the miracle that you are a believer.