ה֥וּא אַהֲרֹ֖ן וּמֹשֶׁ֑ה אֲשֶׁ֨ר אָמַ֤ר יְהוָה֙ לָהֶ֔ם הוֹצִ֜יאוּ אֶת־בְּנֵ֧י יִשְׂרָאֵ֛ל מֵאֶ֥רֶץ מִצְרַ֖יִם עַל־צִבְאֹתָֽם׃
These are that Aaron and Moses, to whom the LORD said: ‘Bring out the children of Israel from the land of Egypt according to their hosts.’
Rashi on Exodus
הוא אהרן ומשה THESE ARE THAT AARON AND MOSES who are mentioned above where it states (v. 20) that Jochebed bore them to Amram. הוא אהרן ומשה There are some passages where Scripture mentions Aaron before Moses (as here) and other passages where it mentions Moses before Aaron; this is done in order to indicate that they were equal in all respects (more lit., that they weighed alike) (Mekhilta d'Rabbi Yishmael 12:1).
Rashbam on Exodus
הוא אהרן ומשה, Aaron, the one born prior to Moses is described as הוא, i.e. a distinction, whereas the same distinction expressed by the same word הוא is also applied to Moses . Both were singled out as G’d’s messengers.
Sforno on Exodus
הוא אהרן ומשה, repeated, seeing these two were the most honoured of their families and it was therefore they who were fit to be entrusted by G’d with the command: הוציאו את בני ישראל, seeing that their voices would be heeded by their compatriots, of all the various tribes.