Augustine reads Psalm 90 as Moses’ prayer, interpreting Moses both as minister of the Old Testament and prophet of the New. The psalm’s reference to generations therefore points toward the unity of the two covenants, with Moses’ witness directing readers to Christ. Against the mutability of creation and human life, Augustine sets God’s eternal, immutable “Is,” the believer’s secure refuge. The petitions for God’s help correspond to the Lord’s Prayer: amid temptation, human beings need grace to turn their hearts toward eternal things.

The comparison of a thousand years with a day or a watch rejects calculations of prophetic chronology and recalls the transience of earthly existence. Human life is grass that withers, marked by sin, suffering, fear of death, and divine scrutiny. Even Christ’s sorrow before death gives mortal weakness a path toward faithful endurance and martyrdom. The seventy and eighty years of the psalm receive symbolic readings connected with the Old and New Testaments; labor and sorrow become discipline through which God’s mercy perfects the weak. Apparent prosperity may conceal divine anger, whereas chastisement can preserve the sinner from condemnation. God’s “right hand” is Christ, whose revelation teaches believers to seek eternal rather than temporal rewards. Bound by the “golden chains” of wisdom, the faithful endure persecution and cry for the morning when they will see God. Their good works become righteous when directed by love, the Law’s fulfillment, and Christ unveils the eternal hopes hidden in Moses’ words.