“As the people were in expectation, and all were questioning in their hearts concerning John, whether he might be the Christ, John answered them all, saying, ‘I baptize you with water, but he who is mightier than I is coming, the strap of whose sandals I am not worthy to untie. He will baptize you with the Holy Spirit and fire. His winnowing fork is in his hand, to clear his threshing floor and to gather the wheat into his barn, but the chaff he will burn with unquenchable fire’” (Luke 3:15-17, ESV).
The good news about Jesus is always accompanied by what some might consider “bad news.”
While John the Baptist preached the good news that God was sending a Savior, the Messiah, to redeem His people, he also told people to stop their bad behavior (Luke 3:7-14). And he reproved Herod, the ruler over Galilee, for all the evil things he had done (vs. 19).
Basically, John declared that to receive the good news of Jesus and be baptized necessitated a change in behavior, which was bad news for some.
To those reluctant to change their ways or who liked their evil lifestyle, as did Herod, John’s message was a good news/bad news scenario.
The “good news” is that you have a Savior, Jesus Christ, who can redeem you from sin and for eternal life, but the “bad news” is that when He does, it will change your lifestyle and behavior because “He will baptize you with the Holy Spirit and with fire” (Luke 3:16).