Deuteronomy 4:35

הראת — Understand this as the Targum has it: Thou hast been shown. When the Holy One, blessed be He, gave the Torah, He rent open to them the seven heavens, and just as he rent open the higher regions so did He rend open the lower, so that they saw that He was alone (sole God). On this account it is stated, "Thou hast been shown that thou mayest know [that the Lord is God, there is none besides Him]" (Pesikta Rabbati 20 towards the end).

אַתָּה֙ הׇרְאֵ֣תָ לָדַ֔עַת כִּ֥י יְהֹוָ֖ה ה֣וּא הָאֱלֹהִ֑ים אֵ֥ין ע֖וֹד מִלְּבַדּֽוֹ׃

To thee it was shown, that thou mightest know that the Lord he is God; there is none else beside him.