Hashem instructs Moshe to command Aaron and his sons, during their seven days of training, concerning their ongoing role in the Mishkan’s sacrificial rites.
“You shall not leave the entrance of the Mishkan for seven days, until the day when your days of inauguration are completed: for you shall be inaugurated for a seven-day period.” (Sefer Vayikra 8:33 rendered to English in the Artscroll Stone Chumash)