Luke 3:5

Every valley shall be filled, and every mountain and hill shall be bought low; and the crooked shall be made straight, and the rough ways shall be made smooth. S. Gregory (Hom. xx. In Evangelia), S. Augustine, S. Chrysostom, Bede, and others interpret these words as meaning, Every one that exalteth himself shall be humbled, and he that humbleth himself shall be exalted, as Christ said. This, however, is a discourse in which John exhorts his hearers to a change of life and conversation, as though he said, 0 ye Jews, prepare the way for Christ, your Messiah, now about to come to you. Wherefore, "Every valley shall be filled," i.e., let it be filled up, "and every mountain and hill shall be brought low," i.e., let it be brought low, "and the crooked," i.e., difficult ways, "shall be," i.e., let them be made, "into straight," &c. In other words, smooth all the ways for Christ, your King, Who cometh, as is wont to be done for kings that are about to enter upon their kingdoms, so that the rough ways be made smooth and level. Remove from your minds all that is evil, distorted, or unequal; too much lifted up, or too much cast down; he that beareth in his heart the mountain of pride, let him bring down this swelling, and he that hath in him the valley of pusillanimity or sloth, let him lift and fill it up with generosity and confidence in God; and he that is of "rough" behaviour, let him train himself to suavity and modesty.

And all flesh shall see the salvation of God i.e., so shall it come to pass that every man shall be able to see both with the eyes of the body, and also more especially with those of the soul, "the salvation of God" the Saviour Christ feel and experience within himself the salvation and the power of the grace brought by Christ.

S. Gregory (Hom. 20 In Evang.) says, "Every valley shall be filled up, because the humble receive a gift which the hearts of them that are puffed up repel from them. The bad places are made straight when the hearts of the wicked, turned awry by iniquity, are directed by the rule of justice; and the rough places are turned into smooth ways when haughty and angry minds return to the gentleness of meekness by the infusion of heavenly grace."

The verses from 7 to 10 have been explained in the Commentary on S. Matthew 3:7. Ver. 10. And the people asked him, saying, What shall we do then? that we may bear fruits worthy of penance, and so avoid the ruin threatened by you, and obtain everlasting salvation. John had accused the Pharisees and the populace, but the Pharisees "despised the counsel of God," c. vii. 30, and therefore also the discourse of John; but the crowd of common people, deeply moved and touched by the force of his preaching, try to find out the way to repent, so as to seize upon John's instructions, and offer themselves to him ready and prepared. So also, in these days, the common people were more ready than the great to take hold of the warnings of preachers, and are therefore saved rather than they.