How come that Moshe did not know the Halachah?
Rashi #1: He forgot the Halachah because, after appointing judges in the time of Yisro, he said to them "Whatever is too difficult for you bring to me ... ". 1
Rashi #2: This Parshah was fit to have been said through Moshe, and it is because the B'nos Tz'lofchad were meritorious that it was said through them. 2
Targum Yonasan: Moshe actually knew the answer, and he claimed not to know it to teach the heads of Sanhedrin who would follow him not to be ashamed to say 'I don't know'. 3