Psalm 90, the oldest of the psalms, goes back to the historic roots of Israel to remind us of Yahweh’s faithfulness despite the darkness of Psalms 88 y 89, “Lord, you have been our dwelling place in all generations” (Psalm 90:1). Here Moses reminds us that God is exalted, greater and more glorious than creation or time, “Before the mountains were brought forth, or ever you had formed the earth and the world, from everlasting to everlasting you are God… For a thousand years in your sight are but as yesterday when it is past, or as a watch in the night” (Psalm 90:2, 4). On the other hand, we human beings are like a dream, like grass that flowers in the morning but by afternoon, is faded and withered (Psalm 90:5-6).
One of the main reasons for the vast difference between Yahweh’s glory and our impermanence is sin, “You have set our iniquities before you, our secret sins in the light of your presence” (Psalm 90:8). Therefore, the appropriate response of all human beings first and foremost is repentance, “Return, O children of man!” (Psalm 90:3) Afterwards, with a humble and contrite heart, we can be guided by Yahweh, “So teach us to number our days that we may get a heart of wisdom” (Psalm 90:12).
Recognizing that Yahweh is exalted while we are sinners in need of repentance, Moses now can ask the same question that disturbed the psalmist in Psalm 89:46, “Return, O LORD! How long?” (Psalm 90:13) But Moses sends his cry along another path than the psalmist Ethan the Ezrahite in Psalm 89. Instead of crying out according to the Davidic covenant, Moses returns to the roots of the covenant given in Exodus and requests that Yahweh’s righteous anger be propitiated according to His abundant mercy: “Have pity on your servants! Satisfy us in the morning with your steadfast love, that we may rejoice and be glad all our days” (Psalm 90:13-15). He intercedes for Israel according to the mercy of Yahweh, our exalted and faithful God.
And the rest of Book Four continues along these notes. References to King David and the Davidic covenant almost completely disappear. In the midst of the tribulation of the anointed one, Psalms 90 – 106 return to Yahweh’s eternity and His eternal mercy: “He has broken my strength in midcourse; he has shortened my days. ‘O my God,’ I say, ‘take me not away in the midst of my days – you whose years endure throughout all generations!’ Of old you laid the foundation of the earth, and the heavens are the work of your hands. They will perish, but you will remain; they will all wear out like a garment. You will change them like a robe, and they will pass away, but you are the same, and your years have no end” (Psalm 102:23-27).
They remind us of Yahweh’s past mercies, the ones that shone forth in the years before David, “Remember the wondrous works that he has done, his miracles, and the judgments he uttered, O offspring of Abraham, his servant, children of Jacob, his chosen ones!” (Psalm 105:5-6)
They invite us to learn from His past mercies to avoid punishment for complaining and rebellion: “Do not harden your hearts, as at Meribah, as on the day at Massah in the wilderness, when your fathers put me to the test and put me to the proof, though they had seen my work. For forty years I loathed that generation and said, ‘They are a people who go astray in their heart, and have not known my ways.’ Therefore I swore in my wrath, ‘They shall not enter my rest’” (Psalm 95:8-11).
Then with faith firmly anchored in Yahweh’s former mercies, the fourth book responds to the desperation of the third by recognizing His mercies behind-the-scenes even in the midst of tribulation: “Nevertheless, he looked upon their distress, when he heard their cry. For their sake he remembered his covenant, and relented according to the abundance of his steadfast love. He caused them to be pitied by all those who held them captive” (Psalm 106:44-46).
Therefore the fourth book ends with a secure faith in Yahweh’s future mercies: “Save us, O LORD our God, and gather us from among the nations, that we may give thanks to your holy name and glory in your praise. Blessed be the LORD, the God of Israel, from everlasting to everlasting! And let all the people say, ‘Amen!’ Praise the LORD!” (Psalm 106:47-48).
In this way the fourth book of the Psalms gives us a powerful prescription to counteract the depression and spiritual listlessness that come with tribulation. It teaches us to contemplate Yahweh’s exaltedness, focusing above all on His mercy. As we recall His past mercies, we look for evidence of His hands at work in present suffering and cry out to Him with a secure faith in expectation of His future mercies.