Psalms 126:4

"Turn our captivity, O Lord, as the torrents in the south" (ver. 4). Consider, my brethren, what this meaneth. ...As torrents are turned in the south, so turn our captivity. In a certain passage Scripture saith, in admonishing us concerning good works, "Thy sins also shall melt away, even as the ice in fair warm weather." Our sins therefore bound us. How? As the cold bindeth the water that it run not. Bound with the frost of our sins, we have frozen. But the south wind is a warm wind: when the south wind blows, the ice melts, and the torrents are filled. Now winter streams are called torrents; for filled with sudden rains they run with great force. We had therefore become frozen in captivity; our sins bound us: the south wind the Holy Spirit hath blown: our sins are forgiven us, we are released from the frost of iniquity; as the ice in fair weather, our sins are melted. Let us run unto our country, as the torrents in the south. ...

Therefore, the devil and his angels, by turning from the light and warmth of charity and going over to pride and envy, were made numb as by an icy hardness. Therefore they are figuratively located in the north. Thus, while the devil weighed down the human race, the future grace of the Savior was spoken of in the Canticle of Canticles thus: "Arise, O north wind, and come, O south wind, blow through my garden and let the aromatical spices thereof flow." Arise, you who did rush in, who does weigh on the conquered, who does oppress those whom you own, arise, that those whose souls you have pressed on and bowed down may be relieved of your weight and may lift up their heads. "And come, O south wind," he says, calling on the spirit of grace, breathing from the south, as from a warm and luminous quarter, "that the aromatical spices may flow." Hence the apostle says, "We are the good odor of Christ in every place." Hence, also, it says in another psalm, "Turn again our captivity, O Lord, as a stream in the south"; doubtless, the captivity in which they were held under the devil, as under the north wind, where they were chilled by abounding iniquity, and were, so to speak, frozen. Hence, also, the Gospel says, "And because iniquity has abounded, the charity of many shall grow cold." But, truly, when the south wind blows, the ice is melted and the streams flow; that is, when their sins are forgiven the people flock to Christ by charity. Hence, also, it is written elsewhere, "And your sins are melted away as the ice in the fair, warm weather."