Midrash su Isaia 40:23

“I saw all the work of God, as man is unable to discover the work that is performed under the sun. Although man toils to seek, he will not find; even if a wise man will wish to know, he will not be able to find” (Ecclesiastes 8:17).
“I saw all the work of God.”⁴⁶This is understood as a reference to mitzvot. The continuation of the verse indicates that man will never understand everything about Torah and mitzvot. Rabbi Pinḥas and Rabbi Yirmeya [said] in the name of Rabbi Ḥiyya bar Abba: Many sought to perform and fathom the Torah, but were unable to do so. What is the reason? “Although man toils to seek, he will not find.” “Even if a wise man will wish” – this is Solomon on the day that he said: I am able to amass⁴⁷Many wives. without straying.⁴⁸He did so despite it being contrary to the verse: “He shall not amass wives, and his heart will not stray” (Deuteronomy 17:17).
Rabbi Yehoshua of Sikhnin said in the name of Rabbi Levi: It is written: “Who renders princes into nothing” (Isaiah 40:23) – this is Moses. At the moment that he said: “The matter that is too difficult for you, [bring to me and I will hear it]” (Deuteronomy 1:17), the Holy One blessed be He said to him: ‘Moses, you judge the difficult [cases]? I will bring you a case that the disciple of your disciple can judge, and even women, but you will be unable to resolve it.’ Which [case] is that? This is the case of the daughters of Tzelofḥad. The Rabbis say: God forbid; Moses was not arrogant. Rather, this is what he said: “The matter that is too difficult for you” – if I have clear knowledge of it, “I will hear it.” If not, I will refer it to God.