How do we know regeneration is necessary for salvation?

The necessity of regeneration for salvation is rooted in the understanding that human effort and decision-making cannot bring about the true change required for salvation. In Galatians 1:15-16, Paul writes about being called by God's grace to reveal His Son in him, illustrating that it is not enough to have superficial knowledge or make decisions for Christ; rather, one must experience the inner work of the Holy Spirit. This regeneration leads to a profound heart transformation, which results in a genuine faith and relationship with God. Without the work of the Holy Spirit to regenerate the believer, they remain in their fallen state, unable to fulfill God’s commands or truly know Him.