Luke 3:7-18: He will baptize you with the Holy Spirit and fire
(NRSV) John said to the crowds that came out to be baptized by him, 'You brood of vipers! Who warned you to flee from the wrath to come? Bear fruits worthy of repentance. Do not begin to say to yourselves, "We have Abraham as our ancestor"; for I tell you, God is able from these stones to raise up children to Abraham. Even now the axe is lying at the root of the trees; every tree therefore that does not bear good fruit is cut down and thrown into the fire.'
And the crowds asked him, "What then should we do?" In reply he said to them, 'Whoever has two coats must share with anyone who has none; and whoever has food must do likewise.' Even tax-collectors came to be baptized, and they asked him, 'Teacher, what should we do?' He said to them, 'Collect no more than the amount prescribed for you.' Soldiers also asked him, 'And we, what should we do?' He said to them, 'Do not extort money from anyone by threats or false accusation, and be satisfied with your wages.'
As the people were filled with expectation, and all were questioning in their hearts concerning John, whether he might be the Christ, John answered all of them by saying, 'I baptize you with water; but one who is more powerful than I is coming; I am not worthy to untie the thong of his sandals. 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 granary; but the chaff he will burn with unquenchable fire.'
So, with many other exhortations, he proclaimed the good news to the people.
As John sees it, too much of Israel relies on the knowledge that having Abraham as an ancestor is sufficient righteousness. Not so, he says, for if He wishes God may raise up stones and declare them children of Abraham. The lineage itself is not dispositive. John is asked repeatedly, "What must we do?" What does God expect and demand? He tells them, do justice. Show mercy. Do not proclaim a false witness against another. The words he spoke were amplified throughout eternity by the One whose arrival he proclaimed.