Albert Barnes Commentary Psalms 144:15

"Happy is the people that is in such a case; [Yea], happy is the people whose God is Jehovah." — Psalms 144:15 (ASV)

Happy is that people that is in such a case - In such a condition; or, where these things prevail.

Yea, happy is that people, whose God is the Lord - Whose God is Yahweh; who worship and serve Him as their God. The worship of Yahweh — the religion of Yahweh — is “adapted” to make a people happy; peaceful; quiet; blessed. Prosperity and peace, such as are referred to in the previous verses, are, and must be, the result of pure religion. Peace, order, abundance, attend it everywhere, and the best security for a nation’s prosperity is the worship of God; that which is most certain to make a nation happy and blessed is to acknowledge God and to keep His laws.