Deeper Commentary

Psa 117:1

Praise Yahweh, all you nations! Extol Him, all you peoples!- The invitation is to the Gentile nations to praise God because of His grace toward "us", Israel (:2). This is after the pattern of how David proclaimed to the Gentile world his experience of grace, and thereby urged them to also accept Yahweh as the God of all grace. His pattern was to be that of all Israel. It is part of the "Hallel Psalms" (Ps. 111-118), chants sung at the feasts of Passover, Pentecost and Tabernacles, which consist of Psalm 113-118.

Psa 117:2

For His grace is great toward us, Yahweh’s faithfulness endures forever. Praise Yah!-
The same word used for how David's sins "overwhelmed me" (Ps. 65:3) is used of how overwhelming or "great" is God's grace (Ps. 103:11; 117:2). David felt overwhelmed firstly by his sin and then by God's grace. This explains his fragile emotional and nervous state, as often reflected in the Psalms. But his path is to be that of all God's true Israel.