What is regeneration, according to the Bible?

Regeneration is the work by which God the Holy Spirit makes us spiritually alive (Titus 3:5; Eph. 2:4–6). We are born again as children of God (1 Pet. 1:23; John 3:3–7; 1:12, 18), having been identified with Christ in His death, burial, and resurrection (Rom. 6:3–4) and seated with Him in Heaven (Eph. 2:4–7; Col. 3:1–4). Before regeneration, we were physically alive but spiritually dead; now we are spiritually alive in Christ and positionally dead to the flesh (John 5:21; Rom. 6:13). Eternal life has been imputed to us, and we have been transferred from the domain of darkness to the kingdom of light (1 John 5:12; Col. 1:13). Regeneration is a new birth, where we are made spiritually alive through faith in Jesus Christ, resulting in a new position and identity as children of God.