baptism.

Matthew 3:1
In those days John the Baptist came, preaching in the wilderness of Judea

Matthew 11:7-15
As John's disciples were leaving, Jesus began to speak to the crowds about John: "What did you go out into the wilderness to see? A reed swaying in the wind? . . .

Matthew 17:12, 13
But I tell you that Elijah has already come, and they did not recognize him, but have done to him whatever they wished. In the same way, the Son of Man will suffer at their hands." . . .

Mark 1:1-11
This is the beginning of the gospel of Jesus Christ, the Son of God. . . .

Mark 11:27-33
After their return to Jerusalem, Jesus was walking in the temple courts, and the chief priests, scribes, and elders came up to Him. . . .

Luke 1:11-17, 67-80
Just then, an angel of the Lord appeared to Zechariah, standing at the right side of the altar of the incense. . . .

Luke 3:2-20
during the high priesthood of Annas and Caiaphas, the word of God came to John son of Zechariah in the wilderness. . . .

Luke 7:28-35
I tell you, among those born of women there is no one greater than John, yet even the least in the kingdom of God is greater than he." . . .

John 1:6, 15, 25-34
There came a man who was sent from God. His name was John. . . .

John 3:26-36
So John's disciples came to him and said, "Look, Rabbi, the One who was with you beyond the Jordan, the One you testified about--He is baptizing, and everyone is going to Him." . . .

Why.

Luke 20:5
They deliberated among themselves and said, "If we say, 'From heaven, ' He will ask, 'Why did you not believe him?'

John 3:18
Whoever believes in Him is not condemned, but whoever does not believe has already been condemned, because he has not believed in the name of God's one and only Son.

John 5:33-36, 44-47
You have sent to John and he has testified to the truth. . . .

John 10:25, 26
"I already told you, " Jesus replied, "but you did not believe. The works I do in My Father's name testify on My behalf. . . .

John 12:37-43
Although Jesus had performed so many signs in their presence, they still did not believe in Him. . . .

1 John 3:20
If our hearts condemn us, God is greater than our hearts, and He knows all things.