Repent ye: for the kingdom of heaven is at hand… and He will throughly purge His floor, and gather His wheat into the garner; but He will burn up the chaff with unquenchable fire.- Matthew 3:2, 12

“Repent! Repent ! Repent!” was John’s continual cry. This awakened the consciences of his hearers concerning their sin. Preaching repentance meant, “You have sinned; change your mind in reference to that sin. You have sinned; quit the sin, mourn over it, ask forgiveness for it. Repent ye!” Whenever a man brings to the minds of others their sins, when he so does it that they begin to feel that they have sinned, then they are being prepared for the Lord, for no man will come to the Saviour unless he knows that he needs a Saviour; and no man will feel that he needs a Saviour until he feels that he is a sinner. Hence it is a real preparation of men for Christ to convince them of sin.

The preacher who would “make ready a people prepared for the Lord” must come out with his axe, and lay it to the root of the trees; he must be definite and distinct in indicating this sin and that sin, and crying to all men, “Repent of these sins. Give them up. Get clear from them. Be washed from them; or else, as God lives, when the Christ Himself comes, it will not be to save you, but to blow you away with His winnowing fan as the chaff is blown into the fire.”

This is “to make ready a people prepared for the Lord” by their being convinced of sin and led to repentance. Hence it is a real preparation of men for Christ to convince them of sin. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2404.cfm