What is the Torah referring to when it writes that Moshe, Aharon and Adas b'nei Yisrael did all that Hashem commanded them?
Rashi: Moshe stood them, Aharon waved them 1 and Yisrael leaned their hands on them.
Seforno: Between them they helped the Levi'im to do everything that needed to be done regarding shaving, washing their clothes and bringing their Korban.
And why does the Pasuk repeat "Kein Asu lahem b'nei Yisrael"?
Seforno: To inform us that Yisrael made an effort to do for the Levi'im whatever needed to be done, in order to carry out the Will of Hashem.