And so he gathered together a people for himself, and fostered them with many liberal distributions of his bounty, and, after so often finding them most ungrateful, ever exhorted them to repentance and sent out the voices of the universal company of the prophets to prophesy. By and by, promising freely the grace which in the last times he was intending to pour as a flood of light on the universal world through his Spirit, he bade the baptism of repentance lead the way, with the view of first preparing, by means of the sign and seal of repentance, them whom he was calling, through grace, to (inherit) the promise surely made to Abraham. 

John holds not his peace, saying, “Enter upon repentance, for now shall salvation approach the nations” — the Lord, that is, bringing salvation according to God’s promise. To him John, as his harbinger, directed the repentance (which he preached), whose province was the purging of men’s minds, that whatever defilement inveterate error had imparted, whatever contamination in the heart of man ignorance had engendered, that repentance should sweep and scrape away, and cast out of doors, and thus prepare the home of the heart, by making it clean, for the Holy Spirit. 

Tertullian