Moshe was given the task to make sure only the best oil was used for the Menorah. “You should command Bnei Yisrael,” said HaShem, “that they shall bring you the finest oil which comes from the first pressing of the olive – only the very first drop is pure enough to light My Menorah. Aharon and his children, the Kohanim, will be in charge of lighting the Menorah – “Tamid” – every single day.”
Once the pure olive oil was collected, it was the job of the Kohanim to prepare the Menorah and light it. Every morning, a Kohen would enter the Kodesh chamber of the Mishkan, where the Menorah stood, and climb the steps in front of it. He would clean out the oil cups from the previous day, replace old wicks with new ones, and pour new oil in so it should burn throughout the entire night. In the afternoon, before dark, the Kohen would light the Menorah once again. He did this every single day of the week, including Shabbos.