Deuteronomy 33:5

וַיְהִי בִישֻׁרוּן מֶלֶךְ בְּהִתְאַסֵּף רָאשֵׁי עָם יַחַד שִׁבְטֵי יִשְׂרָאֵל

He was King in Jeshurun, when the heads of the people were gathered, all the tribes of Israel together.

This verse is one of the Malkiyos – the verses expressing G-d’s kingship – recited as part of Musaf on Rosh Hashana. “He” in the verse refers to G-d and Jeshurun, from the Hebrew word “yashar” (meaning “upright”) refers to the nation of Israel. The Ramban explains that G-d is evident as the Jews’ King when they act like upright individuals and when they gather together in unity. This verse connects to the preceding one, that Moshe delivered the Torah as our inheritance, because that is likewise a fundamental piece of this equation.