Rabbi Yaakov Weinberg zt”l: Notes on Devarim VII: Moshe’s Response
Since Klal Yisrael desired judges, as Rashi in pasuk 14 brings, because they felt that they could bribe them, Moshe set up and found judges that would serve to prevent that. He made the best possible effort to see to it that judges would be ones that would not be affected by bribery, as the pasuk describes. Also, in pasuk 16, Moshe teaches us that before you appoint judges you have to see to it that they know how to perform the job well(which is why Moshe immediately, ‘ba’es hahi’, taught them the halachos of how to judge).
They cannot ‘learn on the job’ as the Rosh Yeshiva ZTL suspects most secular judges do.
U’Shmativ (pasuk 17) Rashi brings on this pasuk that Moshe was punished here because he appeared too confident that he would be able to paskin correctly to ail the shaylos of Klal Yisrael(‘takrivun alaiy’).
The Rosh Yeshiva ZTL would have learned that the word ‘Ushamtiv’ would be showing that Moshe did not have such an intent but rather he was saying that I’ll listen to the shaylos and try to answer. I’ll ask the Ribbono Shel Oiam if I have to.’
But Chazal apparently understand Ushmativ that Moshe was telling them they should not be ashamed to ask anything. They don’t have to worry that Moshe won’t answer or he’ll play games with them to sharpen their minds.
A rebbe is permitted and should at times play games with his talmid’s mind and even withhold answers to questions if he feels that it is for the good of the talmid. But this does not apply when the questions are halachic. When the talmid needs a psak the Rebbe cannot do anything but answer the question. This is how Chazal understood the word Ushmativ.