1)
Why does the Torah need to tell us the ages of Moshe and Aharon?
1.
Rashi (in Sotah 12a): Because it was in the same year that Yisrael left Egypt.
2.
Seforno: To teach us (with reference to the previous Pasuk) that despite their advanced age, 1 they hurried to perform the will of Hashem with alacrity. 2
1
Seforno: Bearing in mind that, already then, eighty was considered passed the stage of 'old age (Seivah)' and into that of 'Gevuros,' as the Pasuk in Tehilim 90:10 - composed by Moshe - teaches us.
2
Oznayim la'Torah: We learn from here the futility of "retirement" to relax and enjoy one's final years in quietude!
