Allegorical Explanation of the Sea and the Fruit-Bearing Earth— Verses 9 and 11
20 Who has gathered the embittered together into one society? For they have all the same end, that of temporal and earthly happiness, on account of which they do all things, although they may fluctuate with an innumerable variety of cares. Who, O Lord, unless Thou, said, Let the waters be gathered together into one place, and let the dry land appear, which “thirsts after You”? For the sea also is Yours, and You have made it, and Your hands prepared the dry land. For neither is the bitterness of men's wills, but the gathering together of waters called sea; for Thou even curbest the wicked desires of men's souls, and fixest their bounds, how far they may be permitted to advance, and that their waves may be broken against each other; and thus dost Thou make it a sea, by the order of Your dominion over all things.
21. But as for the souls that thirst after You, and that appear before You (being by other bounds divided from the society of the sea), them Thou waterest by a secret and sweet spring, that the earth may bring forth her fruit, and, You, O Lord God, so commanding, our soul may bud forth works of mercy according to their kind, — loving our neighbour in the relief of his bodily necessities, having seed in itself according to its likeness, when from our infirmity we compassionate even to the relieving of the needy; helping them in a like manner as we would that help should be brought unto us if we were in a like need; not only in the things that are easy, as in “herb yielding seed,” but also in the protection of our assistance, in our very strength, like the tree yielding fruit; that is, a good turn in delivering him who suffers an injury from the hand of the powerful, and in furnishing him with the shelter of protection by the mighty strength of just judgment.
Source: Confessions (New Advent)