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We learn in Parsha Tzav that for seven days, Moshe taught Aaron HaKohen and his sons the laws of their Avodah in the Mishkan. (You might say that they were given OJT from Shemayim.)
Our Parsha Shemini begins by relating that on the eighth day, Aaron and his sons commenced their Avodah HaKodosh. And it is interesting and ironic that our parsha is the other side of the term; “Tzav-Shemonah” which is the document or order issued by the Israel Defense Forces calling reservists to active duty in event of war.

NOT! 