When is "ba'Eis ha'Hi" referring to?
Ramban: When Yisrael were staying in Chorev, and it refers to the advice of Yisro- before Hashem said to them "Rav lachem Sheves ba'Har ha'Zeh (Pasuk 6). 1
See R. Chavel's notes.
Why did Moshe insert the word "Leimor"?
Rashi: To inform them that what he was about to say was not his personal statement 1 but was dictated by Hashem.
Targum Yonasan: He informed them that he would not leave them to be judged by a single judge.
See Sh'mos 18:18, 19.
How is it possible that Moshe, who took them out of Egypt, split the Sea for them, brought down the Manna and blew in the quails, was unable to judge them?
Rashi: It was not a question of able or unable, but rather one of responsibility - since Hashem placed the people above their judges 1 by taking away the punishment for Yisrael's sins from them and placing it on their judges 2 (their leaders). 3
Rashi: As stated in the following Pasuk.
See Sifsei Chachamim.
Rashi: And a similar statement was later made by Shlomo ha'Melech, when he said in Melachim 1, 3:9 "Ki Mi Yuchal Lishpot Es Amcha ha'Kaved ha'Zeh" - with reference to Jewish judges, as opposed to Nochri judges who are not taken to task for sentencing a defendant to death unjustly or for perverting justice and robbing (See Rashi). If a Jewish judge unjustly extracts money from a litigant, it is considered as if he took his life.
Why did Moshe insert this Pasuk here?
Ramban: He was pointing out that, having received the Torah and appointed judges and policemen to judge them, they were ready to enter Eretz Yisrael. They had indeed traveled from Chorev, the tribes in the order of their flags with their judges and their elders, and when they approached him together with their sages and elders with the request to send spies, everything fell apart.
QUESTIONS ON RASHI
Rashi writes that also Shlomo said "Mi Yuchal Lishpot
Moshav Zekenim, Riva citing R. Tam of Orlins: Since Hashem gave to him extra Chachmah, presumably, he was already a Chacham