Luke 3:5

For when Jesus had come and sent His Spirit, every valley was filled with good works, and the fruits of the Holy Spirit, which if thou hast, thou wilt not only cease to become a valley, but will begin also to be a mountain of God. Or you may understand the mountains and hills to be the hostile powers, which have been overthrown by the coming of Christ.

(non occ.) But as the hills differ from mountains in respect of height, in other things are the same, so also the adverse powers agree indeed in purpose, but are distinguished from one another in the enormity of their offences.

(ubi sup.) Or by the valleys he means a quiet habitual practice of virtue, as in the Psalms, The valleys shall be filled with corn. (Ps. 65:13.) (ubi sup.) Or, He orders the valleys to be filled, the mountains and hills to be cast down, to show that the rule of virtue neither fails from want of good, nor transgresses from excess.

(ubi sup.) He denounces the haughty and arrogant by the name of mountains, whom Christ has brought low. But by the hills He implies the wreckless, not only because of the pride of their hearts, but because of the barrenness of despair. For the hill produces no fruit.

But Luke expresses somewhat further: not repeating the exordium, and so passing on, but setting down likewise all the prophecy. "For every valley," saith he, "shall be filled; and every mountain and hill shall be brought low; and the crooked shall be made straight, and the rough ways smooth; and all flesh shall see the salvation of God." Dost thou perceive how the prophet hath anticipated all by his words; the concourse of the people. Thus, when he saith, "Every valley shall be filled, and every mountain and hill shall be brought low, and the rough ways shall be made smooth;" he is signifying the exaltation of the lowly, the humiliation of the self-willed, the hardness of the law changed into easiness of faith. For it is no longer toils and labors, saith he, but grace, and forgiveness of sins, affording great facility of salvation. Next he states the cause of these things, saying, "All flesh shall see the salvation of God;" no longer Jews and proselytes only, but also all earth and sea, and the whole race of men. Because by "the crooked things" he signified our whole corrupt life, publicans, harlots, robbers, magicians, as many as having been perverted before afterwards walked in the right way: much as He Himself likewise said, "publicans and harlots go into the kingdom of God before you," because they believed. And in other words also again the prophet declared the self-same thing, thus saying, "Then wolves and lambs shall feed together." For like as here by the hills and valleys, he meant that incongruities of character are blended into one and the same evenness of self-restraint, so also there, by the characters of the brute animals indicating the different dispositions of men, he again spoke of their being linked in one and the same harmony of godliness. Here also, as before, stating the cause. That cause is, "There shall be He that riseth to reign over the Gentiles, in Him shall the Gentiles trust:" much the same as here too he said, "All flesh shall see the salvation of God," everywhere declaring that the power and knowledge of these our Gospels would be poured out to the ends of the world, converting the human race, from a brutish disposition and a fierce temper to something very gentle and mild.