How do we know God the Holy Spirit is essential for salvation?

In the context of salvation, the Holy Spirit plays a critical role. According to Titus 3:5, it is through the washing of regeneration and renewing of the Holy Ghost that sinners are saved. The Spirit not only imparts new life but also teaches believers the depth of God's grace and truth. As seen in Galatians 1:15-16, it is through the Holy Spirit that God reveals His Son to the elect, leading to genuine faith in Christ. Without the Holy Spirit's work, the message of salvation remains undiscovered and unfelt.