Why did Lydia need her heart opened by the Lord? She was “a worshiper of God”. She was “listening”.
Reformed doctrine teaches us that man’s condition corrupted by the fall of Adam (through Adam’s sin) is a condition of “total depravity”, the “T” of “TULIP”, the Five Points of Calvinism. We are “dead” in sin. Ephesians 2:1. None of us understands, and none of us seeks God. Romans 3:10-11. We are hostile to God. Romans 8:7 and Colossians 1:21. We are in bondage to sin. Romans 7:14-15.
Because of such “total depravity”, we need such divine action in order to respond faithfully. Jesus said: “No one can come to Me unless the Father who sent Me draws him; and I will raise him up on the last day.” John 6:44. “It is the Spirit who gives life; the flesh profits nothing; the words that I have spoken to you are spirit and are life. “But there are some of you who do not believe ” For Jesus knew from the beginning who they were who did not believe, and who it was that would betray Him. And He was saying, “For this reason I have said to you, that no one can come to Me unless it has been granted him from the Father.” John 6:63-65.
Reformed Doctrine Daily Devotions 