I heard once in a class where the Rabbi taught a teaching from the Vilna Gaon on Tehillim 20:8:
אֵ֣לֶּה בָ֭רֶכֶב וְאֵ֣לֶּה בַסּוּסִ֑ים וַאֲנַ֓חְנוּ ׀ בְּשֵׁם־יְהוָ֖ה אֱלֹהֵ֣ינוּ נַזְכִּֽיר׃
They [call] on chariots, they [call] on horses, but we call on the name of the LORD our God.
I don't remember the details but something to the effect that אלה ברכב is referring to Eisav and אלה בסוסים refers to Yishmael, and something about how the 70 nations (I think the number of words in this chapter) will battle each other in the end of days, led by Eisav (Christianity) and Yishmael (Islam), and we'll only have Hashem.
Where is this teaching found, and what does it say exactly?