What is the Torah telling us, when it writes "Heim ha'Medaberim El Par'oh"?
Rashi: 'They were the ones who were commanded; and they were the ones who carried out the commands.' 1
Seforno: And by the same 2 token, they were the ones whose words would be accepted by Pharaoh.
Gur Aryeh: Rashi is explaining, the expression "Hem" indicates that the people mentioned now are one and the same as those mentioned elsewhere. Rashi tells us where that other mention is - it was when they were commanded to appear before Pharaoh, and bring the Bnei Yisrael out of Mitzrayim (6:13).
Why does the Torah repeat, "Hu Moshe v'Aharon"?
Rashi: To teach us that Moshe and Aharon maintained their level of righteousness 1 from beginning to end. 2
Rashbam (to 6:26): The sequence of this Pasuk and the previous one teaches us that, although the Torah switches the order of their names, 3 they are the same two people.
Targum Yonasan: To inform us that Moshe was the Navi, and Aharon, the Kohen. 4
What is the significance of the word "Hu [Moshe]" - in the singular?
Maharal (Ohr Chadash p. 72): Chazal (Esther Rabah 1:2) enumerate 10 people who are introduced as unique by the word "Hu." Five of these people were righteous, and five were infamous. 1 Moshe's uniqueness was his level in prophecy.
In truth, the Midrash lists six righteous people - including both Moshe and Aharon (in the preceding Pasuk, 6:26). It must be that because Moshe and Aharon were equivalent (see Rashi), they are counted as one. Maharal (ibid.) lines up Moshe and Aharon against the infamous Dasan and Aviram, who are also listed together as one in the Midrash. Compare Maharal (Gevuros Hashem Ch. 19, p. 85); and refer to 2:13:1.01:2 and 2:13:1.03:2