Book III is comprised of Psalms 73 through 89. Many of these psalms lament the bitterness of the Israelites’ exile to Babylon in 597 BC and Jerusalem’s destruction in 587. This is the darkest collection of psalms, with Psalms 88 and 89 forming the Book of Psalms’ nadir, the former lamenting individual lostness, the latter of national lostness. Based on the Book of Psalms’ Hebrew word count, Psalm 88 is also the Psalms’ midpoint. So it’s as if the psalmists gradually lead us down into the valley of failure and tragedy and then bring us back up out into the light in Books IV and V.
Psalm 89 is especially significant as it voices the psalmist’s anguished cry that the Davidic covenant has ended in utter failure. But while the Davidic covenant failed in its traditional sense–as all merely human institutions do fail us–Isaiah predicted that “a shoot would grow out of the stump of Jesse” when God would restore his people (Isa. 11:1). And indeed, Books IV and V leave us in no doubt that the failure of David’s dynasty couldn’t stop God from fulfilling his plan to bless all the nations through Abraham’s family (Gen. 12:1-3).