Matthew Henry Commentary Luke 3:15-20

"And as the people were in expectation, and all men reasoned in their hearts concerning John, whether haply he were the Christ; John answered, saying unto them all, I indeed baptize you with water; but there cometh he that is mightier than I, the latchet of whose shoes I am not worthy to unloose: he shall baptize you in the Holy Spirit and [in] fire: whose fan is in his hand, thoroughly to cleanse his threshing-floor, and to gather the wheat into his garner; but the chaff he will burn up with unquenchable fire. With many other exhortations therefore preached he good tidings unto the people; but Herod the tetrarch, being reproved by him for Herodias his brother`s wife, and for all the evil things which Herod had done, added this also to them all, that he shut up John in prison." — Luke 3:15-20 (ASV)

John the Baptist disowned being the Christ himself but confirmed the people in their expectations of the long-promised Messiah. He could only exhort them to repent and assure them of forgiveness upon repentance; however, he could not work repentance in them, nor confer remission on them.

It is fitting for us to speak so highly of Christ, and so humbly of ourselves. John could do no more than baptize with water, as a sign that they ought to purify and cleanse themselves. But Christ can, and will, baptize with the Holy Ghost; He can give the Spirit to cleanse and purify the heart, not only as water washes off the dirt on the outside, but as fire clears out the dross that is within and melts down the metal, so that it may be cast into a new mold.

John was an affectionate preacher; he pleaded earnestly; he pressed matters home to his hearers. He was a practical preacher; spurring them to their duty and directing them in it. He was a popular preacher; addressing the people according to their capacity. He was an evangelical preacher.

In all his exhortations, he directed people to Christ. When we press duty upon people, we must direct them to Christ for both righteousness and strength. He was a copious preacher; he did not hesitate to declare the whole counsel of God. But a full stop was put to John's preaching when he was in the midst of his usefulness. Herod, having been reproved by him for many evils, shut John up in prison.

Those who injure the faithful servants of God add even greater guilt to their other sins.