Parashas Vayeilech · Passuk 31:7
Then Moses called Joshua and said to him in the sight of all Israel: Be strong and courageous, for you shall go with this people into the land that the LORD swore to their fathers to give them, and you shall put them in possession of it.
Torah Temimah points to Sanhedrin 8a (סנהדרין ח' א').
English: I am disqualified to judge for you, because I may be partial to you due to what you’ve done for me. Rav said to Rav Kahana: Go out and judge the case. Rav Kahana saw that Rav’s host was acting haughtily due to his relationship with Rav, as he presumed that Rav Kahana was predisposed to favor him. Rav Kahana said to the host: If you are prepared to listen, then listen to me and follow my instructions. And if not, I will take Rav out of your ears. I will treat you harshly, and you will understand that your relationship with Rav will not help you at all. § The Gemara continues to interpret clauses from the verse cited above. “You shall hear the small and the great alike” (Deuteronomy 1:17). Reish Lakish says: This teaches that the judgment of one peruta should be as dear, i.e., important, to you as the judgment of one hundred maneh, i.e., ten thousand dinars. The Gemara asks: With regard to what halakha is this said? If we say it is with regard to the need to study it carefully and to decide the case justly, it is obvious that even cases relating to small sums must be judged thoroughly. Rather, Reish Lakish was speaking with regard to giving it precedence: The small claims case may not be deferred in favor of the larger claim merely because the disputed sum is smaller. The Gemara continues the interpretation of the verse: “You shall not be afraid before any man.” Rabbi Ḥanan says: Do not suppress your statement of opinion due to any person. The verse continues: “For the judgment is God’s.” Rabbi Ḥama, son of Rabbi Ḥanina, says: The Holy One, Blessed be He, says: It is not enough for the wicked judges, that they take money from this person and they give it to that person unlawfully, but they even trouble Me to return the money to its rightful owners. As proper justice is ultimately in the hands of God, He takes responsibility to bring about the rectification of the errors of unfit judges. The verse continues: “And the cause that is too hard for you, you shall bring to me, and I will hear it.” Rabbi Ḥanina, and some say Rabbi Yoshiya, says: On account of this matter, which displayed a degree of presumptuousness, Moses was punished, as it is stated: “And Moses brought their cause before the Lord” (Numbers 27:5). In this instance, when Zelophehad’s daughters presented their case to Moses, he did not know the answer himself and was compelled to ask God. Rav Naḥman bar Yitzḥak objects to this critique of Moses: Is it written: “And I will tell you,” which would indicate that Moses assumed the authority for himself? No, it is written: “And I will hear it,” meaning: If I have learned the halakha, I have learned it. And if not, I will go and learn it. Consequently, there was no presumptuousness in Moses’ statement.
Derash on the verse (Bavli sugya) — not a formal named middah of the 13
The Gemara uses this passuk inside a sugya (question, proof, or illustration). That is classical derash, but not labeled here as one of R' Yishmael’s 13 unless the move is explicit.
Moshe’s charge to Yehoshua is a model of public appointment and encouragement: strength and courage are commanded because the people and the task can intimidate even a worthy successor.