Charles Ellicott Commentary Psalms 117:1-2

"O praise Jehovah, all ye nations; Laud him, all ye peoples. For his lovingkindness is great toward us; And the truth of Jehovah [endureth] for ever. Praise ye Jehovah." — Psalms 117:1-2 (ASV)

This, shortest of all the psalms, might well be called multum in parvo, for in its few words it contains, as St. Paul felt (Romans 15:11), the germ of the great doctrine of the universality of the Messianic kingdom. There can be no doubt that it was intended for liturgical use, and possibly it is only one of the many varieties of the Hebrew Doxology.

Also very noticeable is the ground on which all the world is summoned to join in the praise of Jehovah—His covenant kindness and the fulfillment of His promises to Israel. The idea latent in this is shown in the second word rendered praise; properly, to soothe. The nations are imagined coming to make their peace with Israel’s God after seeing His display of power for their sakes; but a wider and nobler truth emerged from this.