"[Jesus] will baptize you with the Holy Spirit and fire.... He will gather the wheat into His barn, but the chaff He will burn up with a fire that never goes out" (Luke 3.16,17).

Only God can forgive sins so when Luke 3.3 says John preaches "baptism of repentance for forgiveness of sins" John is the "voice of one crying in the wilderness: prepare for the way of the Lord [Jesus]" (Luke 3.4). Forgiveness is realized through faith in Jesus only. Repentance is the precursor to truly accepting Jesus for forgiveness of sins. Forgiveness is not achieved apart from Jesus, e.g. forgiving a friend for mistreating you. Thus, "everyone will see the salvation of God" (v.6) in Christ.

This in the larger context of Is. 40-66, the significance of Jesus as the Savior of all humanity is a reoccurring theme in Luke (1.76-79; 2.11-14,29-32).

Luke did not teach universalism but salvation extended beyond Jews to the Gentiles (see Acts 11.18).