Psalm 67:3–5 (ESV)
Let the peoples praise you, O God;
let all the peoples praise you!
Let the nations be glad and sing for joy,
for you judge the peoples with equity
and guide the nations upon earth. Selah
Let the peoples praise you, O God;
let all the peoples praise you!
—Psalm 67:3–5

The 67th psalm opens with a self-benediction, “May God be gracious to us and bless us and make his face to shine upon us.” We all pray this way, seeking God’s blessing, but it is the benedictory form, “May…,” that seems out of sorts. The grammar is familiar. It is the form of address to oneself that is striking.
You might well recognize the vocabulary of the Aaronic blessing. It will be helpful to recall it in its fuller context.
“The LORD spoke to Moses, saying, “Speak to Aaron and his sons, saying, Thus you shall bless the people of Israel: you shall say to them, The LORD bless you and keep you; the LORD make his face to shine upon you and be gracious to you; the LORD lift up his countenance upon you and give you peace. ‘So shall they put my name upon the people of Israel, and I will bless them’” (Numbers 6:22–27).
The priest pronounces the benediction on the people—that is the norm. That is what we expect. Israel here is not only acting like a priest, she is acting like a priest pronouncing a benediction on herself.
Israel pronounces the Aaronic blessing on herself for the sake of the Abrahamic blessing (v. 2). “May God be gracious to us and bless us and make his face to shine upon us, that your way may be known on earth, your saving power among all nations.” God made a covenant with Abraham saying, “I will make of you a great nation, and I will bless you and make your name great, so that you will be a blessing. I will bless those who bless you, and him who dishonors you I will curse, and in you all the families of the earth shall be blessed” (Genesis 12:1–3) God then redeems the children of Abraham out of Egypt to be a kingdom of priests. At Sinai God spoke to them saying, “Now therefore, if you will indeed obey my voice and keep my covenant, you shall be my treasured possession among all peoples, for all the earth is mine; and you shall be to me a kingdom of priests and a holy nation…” (Exodus 19:5–6). As a kingdom of priests, Israel was to mediate God’s blessing on the nations.
The latter portion of Isaiah speaks of the true servant Israel, a singular person, who will gather Israel back to God. He is everything Israel failed to be. He is the true servant of Yahweh, and Yahweh says to Him, “I will make you as a light for the nations, that my salvation may reach to the end of the earth” (Isaiah 49:6) This is what Israel as a kingdom of priests was to be—a light for the nations, that His salvation might reach to the end of the earth.
Israel pronounces the Aaronic blessing on herself for the sake of the Abrahamic blessing. Even so, this benediction, for this purpose, might bother us—it might well bother us if we suspected that this was all that was desired. It is like the parent that seeks self-blessing for the good of their children. Selfishness might still be in play. Such a prayer may be an expression of idolatry. It is too easy to miss the point of this self-benediction for what is really only a means to the point. It is too easy to take the secondary for the primary.
Israel does not pronounce this self-benediction simply for the benefit of the nations. She asks to be blessed of the Lord, that His way might be known on earth and His saving power among all the nations. That is what missions is about. Is is not about the nations of the earth. It is about the Lord of the nations. That is why the refrain of this psalm is not, “refrain, “Save the peoples, O God; save all the peoples” but rather, ““Let all the peoples praise you, O God; let all the peoples praise you.”