Augustine. Exposition on the Book of Psalms. Schaff, Philip (editor). New York: Christian Literature Publishing Co, 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 plunges directly into his interpretation of Psalm 98 by pointing out the new song to be sung to the Lord is rightly sung by the new man in Christ (Augustine Psalms, loc. 336009, par. 1). Yet this song is to be sung in all the earth, about God's deeds. Augustine notes the works of the Lord recorded in the Gospels as an example.
Augustine sees God's good works as done by Christ, "the arm of God, and the right hand of God" (Augustine Psalms, loc. 336019, par. 1), and that they are done to show God's glory. In verse two, the glory of God, his good work, is his salvation. Again, Augustine ties this directly to Christ's appearing (Augustine Psalms, loc. 336024, par. 2). This, again, is the mercy and truth referenced in verse three. Again, Augustine applies the idea to Christians, as Israel is pictured as extending throughout the whole earth (Augustine Psalms, loc. 336035, par. 3).
Verses 4-6 call for joyful shouts and melodies to God, using all sorts of instruments. Augustine notes that the trumpets and pipes mentioned are formed by hammering. He ties this concept to tribulation, which shapes the believer in his trust for God (Augustine Psalms, loc. 336046, par. 5). Verse seven continues the concept of trial, as it speaks of the sea being stirred up. Augustine sees this as symbolic of persecutions against Christians, as opponents are provoked by the joyful noise of the Christians (Augustine Psalms, loc. 336070, par. 7).
Augustine sees the metaphor changing in verse eight, as the floods clap in response to God's works. Here he sees the water of the Holy Spirit (Augustine Psalms, loc. 336075, par. 7). The hills also bless the Lord (v. 9). This suggests to Augustine that there are differences in hills. "The good hills, are spiritual greatness; the bad hills, are the swelling of pride" (Augustine Psalms, loc. 336080, par. 8). In this way he explains that some hills tremble before God and some rejoice.
Verse 10 describes God's judgment as just and equitable. The righteous would rejoice in His coming, but the unrighteous would not. Rather, they are called for repentance (Augustine Psalms, loc. 336086, par. 8).