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 assigns Psalm 17 to refer directly to Jesus and slightly less directly to the Church (Augustine Psalms, loc. 320188). Verses 1-2 speak to the righteousness of the one praying, asking that the Lord would look on the Psalmist with favor. Verse three declares that the Lord has found no evil in the Psalmist, and verse four declares that the Psalmist keeps away from the ways of “the destroyer.” Even in times of hardship, the one praying has kept God’s ways (Augustine Psalms, loc. 320194). Augustine finds the guidance for such a walk to be in “the Sacraments and Apostolical writings” (Augustine Psalms, loc. 320200). This is where Christ and His Church stand firmly.
The Psalmist cries out to God who hears (verse 6). He expects that God would show great mercies, which cannot be ignored (verse 7). This is especially important, for the Lord uses his mercy to save those who trust him from the people who deny God. Verses 8-9 speak to the way God can cover and shelter His people (Augustine Psalms, loc. 320207). It is especially important to the Psalmist because the opposers have surrounded him, even casting him out of the city. This Augustine sees as a clear reference to Christ and His cross (Augustine Psalms, loc. 320213). Jesus’ enemies considered his death to be a terrible thing for him but good for them. In fact, it was the opposite. They surrounded the Lord as lions (v. 12) even though it did them no good.
In response to those who would reject God, the Psalmist asks, in verse 13, that the Lord would arise, show his power, rescue his people, and cast down the wicked. They considered God’s power to be absent, but it was only pausing out of mercy (Augustine Psalms, loc. 320220). The men of this world, in verse 14, have their reward in this life. They filled themselves with good things from God, all the while denying His power and grace. They can settle for their earthly comforts. They will have no more (Augustine Psalms, loc. 320226). On the other hand, the Psalmist expects to arrive in God’s righteous presence, and to be able to be filled with satisfaction in God’s presence (Augustine Psalms, loc. 320232).