12 “For the Lord shall give sweetness, and our land shall give her increase”....He will give unto you the sweetness of working righteousness, so that righteousness shall begin to delight you, whom before unrighteousness delighted: so that thou who at first delighted in drunkenness, shall rejoice in sobriety: and thou who at first rejoiced in theft, so as to take from another man what you had not, shall seek to give to him that has not that which you have: and thou who took delight in robbing, shall delight now in giving: thou whom shows delighted, shall delight in prayer; thou who delighted in trifling and lascivious songs, shall now delight in singing hymns to God; in running to church, thou who at first ran to the theatre.
Whence is that sweetness born to you, except from this, that “God gives sweetness”? For, behold, you see what I mean: behold, I have spoken unto you the word of God, I have sown seed in your devout hearts, finding your souls furrowed, as it were, with the plough of confession: with devout attention you have received the seed; think now upon the word which you have heard, like those who break up the clouds, lest the fowls should carry away the seed, that what is sown may be able to spring up there: and unless God rain upon it, what profits it that it is sown?
This is what is meant by “our land shall give her increase.” May He with His visitations, in leisure, in business, in your house, in your bed, at meal-time, in conversation, in walks, visit your hearts, when we are not by. May the rain of God come and make to sprout what is sown there: and when we are not by, and are resting quietly, or otherwise employed, may God give increase to the seeds which we have sown, that remarking afterwards your improved characters, we too may rejoice for your fruit.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)