The beginning of Parshas Tetzeveh (Shemos 27:21) starts off with HaShem telling Moshe how Aharon and his sons will be in charge of lighting the Menorah. Yet, it is only in the next posuk (28:1) that we learn the reason why - because Aharon and his sons have been chosen to serve as the kohanim, performing the sacrifices and other duties in the mishkan.
To me, it would have made more sense for the Torah to place this posuk describing the job of maintaining the oil burning after Aharon and his sons had been appointed as the kohanim, presumably in place of the first born.
Incidentally, for those who follow Rashi and not Ramban, that the Torah text isn't necessarily in chronological order, I think this entire section is a point in team Rashi's favor. If the first born were supposed to be the kohanim, but were only replaced after the Chet Ha'egel, why are they already being "replaced" now?
At any rate, I was only able to check Rashi, who doesn't comment on this seemingly out of order placement of these 2 verses.
Does anyone have any ideas that they've heard/learned?