Luke relates the message (3:7-17) of John the Baptist, the God-appointed predecessor of Christ (3:3-6). In fulfillment of the prophecies in Isaiah 40 and Malachi 3, John was “preaching a baptism of repentance for the forgiveness of sins” (3:3; cf. Mark 1:2-3).
When multitudes came out to be baptized by him, John challenged them about the need to bear fruit in their lives to show that they had truly repented (3:7-14). His challenge included clear statements about future wrath (3:7, 9).
John’s preaching climaxed with a statement of Christ as God’s judicial agent: “His winnowing fork is in His hand to thoroughly clear His threshing floor, and to gather the wheat into His barn; but He will burn up the chaff with unquenchable fire” (3:17; cf. Mark 9:42-49). As the coming Judge, He will both save and destroy.
In 3:18, Luke states that John the Baptist continued to minister the gospel (εὐηγγελίζετο, imperfect indicative) by preaching many other things (πολλὰ μὲν οὖν καὶ ἓτερα παρακαλῶν εὐηγγελίζετο τὸν λαόν). This concluding statement shows that the Spirit recorded John’s identification of Christ as God’s judicial executor (3:17) as the final statement of this record of John’s proclamation of the gospel.
The parallel account in Matthew 3:7-12 ends with the same statement of Christ’s judicial agency. Both Matthew and Luke, therefore, teach that John’s ministry of proclaiming the gospel included proclaiming Christ as Judge.
After centuries of silence, God directed John the Baptist to begin declaring a message that powerfully challenged people to repent and believe (cf. Acts 19:4) in Jesus in view of His judicial work as God’s Christ. The New Testament record shows that later Christ (Matt. 4:17, 23; 5-7) and His apostles (Acts 2) preached the gospel with messages very similar in content.
The precedent established by John’s message as well as the messages of Christ and His apostles argues for the continued evangelistic proclamation of Christ as God’s judicial agent.