You'll notice that the edition I'm using is a Kindle edition of the Ante-Nicene and Post-Nicene Fathers in one electronic volume. In print this series is about 40,000 pages. I'm using the Kindle location numbers that will take a reader to the approximate place in the electronic edition. However, for anyone who wants to track this down in a print edition, the citation to a verse in the Psalm ought to be adequately helpful.
Augustine. Exposition on the Book of Psalms. Schaff, Philip (editor). New York: Christian Literature Publishing Col, 1886. Nicene and Post-Nicene Church Fathers: Series 1: Volume VIII. Re-published 2014, Catholic Way Publishing. Kindle electronic edition, ISBN-13: 978-1-78379-372-3.
Augustine boldly identifies the blessed man of Psalm 1:1 as Christ, who didn’t go into ungodliness as did the first Adam. Though born into the world of sinners he did not remain there, though he could have claimed an earthly kingdome he chose a heavenly one instead (Augustine Psalms, loc. 318410). Verse two continues by identifying the blessed man as the one who delights in God’s law. Augstine describes being “in” the law as freedom, as opposed to the slavery found “under” the law (Augustine Psalms, loc. 318418). The blessed and free Christ is, in verse three, the one planted by water, nourished by the Holy Spirit, who quenches all our thirdst (Augustine Psalms, loc. 318426). Augustine goes on to suggest that another way of seeing the running water could relate to the Apocalypse, where people are referred to as waters. In this scenario the Christ, planted near the streams of sinful humanity, draws people into his roots of discipline. In this way he converts people and makes them fruitful as He is fruitful (Augustine Psalms, loc. 318434).
The Psalmist draws a contrast in verse four, speaking of the ungodly and their nature. They are cast out “from the face of the earth,” which Augustine takes to represent God’s steadfastness (Augustine Psalms, loc.31834). He goes on to apply the idea of the earth to an inheritance of God’s stability in several other passages of Scripture.
Because the ungodly are cast away from the earth and scattered in verse five they will not rise in judgment. Augustine takes this statement to mean not that the ungodly will be judged against, but that they will be deprived of the privilege of making judgment, that which they desire (Augustine Psalms, loc. 318442). The Psalm concludes with the observation that God knows the way of the righteous. This indicates God’s denial of those who are sinners, who trust their own way. Being denied by God is to perish, but being those known by God is to inherit eternal life.