What does the Bible say about the necessity of the Holy Spirit in salvation?

The Bible teaches that natural men are dead in trespasses and sins and unable to respond to the Gospel without the direct intervention of the Holy Spirit. This is evident in passages like Ephesians 2:1, which highlights spiritual death. It is only through the Spirit's illumination that the light of the Gospel can penetrate a person's heart, bringing about regeneration and faith. Scripture affirms that unless the Spirit shines in a man’s heart, he cannot desire or understand the spiritual truths of the Gospel (2 Corinthians 4:6).