Moshe transmitted Hashem’s instructions to Aharon to light the Menorah daily according to the regulations given to him. The Torah then informs us that Aharon did as he was told. Rashi, based on the Midrash, comments the reason we are told that Aharon did as told was to teach us that he did not change anything in the performance of this Mitzvah.
Who would have thought that Aharon would change one iota of the way the Mitzvah had to be performed? However, human nature is such that when someone has to perform an act regularly, repeating it daily, it becomes monotonous and he performs it eventually perfunctorily without enthusiasm and without interest.
This is what the Midrash and Rashi are telling us. Though Aharon had to repeat the Mitzvah of lighting the Menorah every day, one would believe that after the passage of time he would lose interest and just go through the motions without much concentration. This is what the Torah is stressing. Aharon did the Mitzvah every day as if it were the first time, with enthusiasm, with eagerness and with zeal.