A wonderful phrase in this song is ki gavar aleinu chasdo (כִּי גָבַר עָלֵינוּ חַסְדּוֹ), "for strong upon us is His faithful love." The word translated "strong" (גָּבַר) means "prevailing" or "triumphing," and has connotations of masculine strength (i.e., the words "mighty man" (גִּבּוֹר) and "power" (גְּבוּרָה) come from the same root). Because of God's strong love for us and because of His ongoing faithfulness (i.e., emet: אֱמֶת), we are commanded to offer praise and thanks to the LORD. We make our "boast" in God's chesed (חֶסֶד) - His unfailing love - by glorifying and sanctifying His Name... Notice that the word "Hallelujah" (הַלְלוּ־יָהּ) at the end of the psalm is the plural imperative form of the verb halal (הָלַל), meaning to "shine" in radiant gratitude before God. The opening phrase "halelu et Adonai" ("praise the LORD") therefore clearly links the Divine Name YHVH (יְהוָה) with the Name Yah (יָהּ).
The question is raised by the sages as to why the nations of the earth should praise the LORD for God's kindness given to Israel. Rav Yitzchak replied, "The princes of the nations plan countless anti-Semitic schemes to destroy the Jewish people, but our Merciful God always manages to foil their plots. Their secret councils are so well-guarded that the Jewish people are often unaware of all the ways the nations plot to harm them, and therefore they are unaware of how God saves them. Only the wicked nations see clearly how God's kindness to the Jewish people is overwhelming - and therefore, only the nations of the earth can praise Him this way." The chesed of the LORD is "mighty toward us" not only in the past, but "the faithfulness (i.e., truth) of the LORD endures forever," which means that it continues to the present hour unto eternity. As the Apostle Paul affirmed, God's truth is eternal, and His gifts and calling are irrevocable (Rom. 11:29).
Psalm 117 alludes to both the praise of the nations for God's saving acts performed during the Exodus and to the coming reign of the Messiah Yeshua in Zion (the intermediary period of praise to the LORD for Yeshua's first advent is presently reserved for the followers of the Messiah during this age). The words "praise the LORD all nations" (הַלְלוּ אֶת־יְהוָה כָּל־גּוֹיִם) prophetically refers to the acclaim the LORD will receive in the coming millennial kingdom, when the nations will all be converted and given lashon ha-kodesh (the holy language) to praise His Name (Zeph. 3:9; Psalm 86:9). If the nations of the earth are commanded to praise the LORD for His faithfulness to Israel - both for the glory of the Exodus and for the reign of Messiah in Zion - how much more are we to praise His Name and shine our gratitude before Him for the glorious redemption we have in Yeshua? Hallelu-Yah!