Rashi on the Prophets and Writings
Psalms 113
a people of a strange tongue With another language, which is not the Holy Tongue. A similar expression is (Isa. 33:19): “A people of a strange tongue you shall not see, a people of speech too obscure, etc.” The “nun” and the “lammed” are interchangeable, like נִשְׁכָּה, chamber, which is [equivalent to] לִשְׁכָּה, in the Book of Ezra (Neh. 13:7).
Judah became His holy nation He took Judah as the lot of His portion and His sanctity, and even they sanctified His name when they descended into the sea, as the matter that is stated (above 68: 28): “the princes of Judah pelt them with stones.” Similarly, this verse is explained in the Aggadah (Mid. Ps. 114:8): Judah became His holy people, for Nahshon sprang into the sea and said, “I shall descend first,” and that is what [the Psalmist] says: Judah became His holy people.
the Jordan turned backward because all the water of Creation split.
Who created the earth Heb. חולי, Who created the earth. The “yud” is superfluous as מגביהי, משפילי and ההוֹפכי.
into a fountain of water Heb. למעינו. The “vav” is superfluous, as the “vav” in (above 104:11, 20) “the beasts (חיתו) of the forest.”
Not for us Not for us or for the fitness of our deeds shall You do [this] for us. but for Your name give honor So that they should not say, “Where is their God now?”
but they do not feel Heb. ימישון, an expression of (Gen. 27:12): “Perhaps my father will feel me (ימשני).”
Those who fear the Lord These are the proselytes.
You arrive at the cited line; the whole work is yours to read around it. The text is set from the cited public-domain edition.