The first section of Parshas Tzav features the tasks of Kohanim which pertain to korbonos (sacrifices), such as Terumas Ha-Deshen (clearing the ashes from the Altar), maintaining the flames on the Mizbe’ach (Altar), and the general role of Kohanim in various korbonos. The second section of Parshas Tzav depicts the investiture (the "Milu'im") of Aharon and his sons into the Kehunah (Priesthood).

It is interesting that the parshah is sequenced this way, as one would expect the Kohanim to first be invested, and to then be commanded the details of the korbonos. Why is the order in the reverse?

The Milu'im process was supremely elaborate. It was a seven-day undertaking that entailed extremely detailed procedures with several korbonos, and it also featured washing the Kohanim, anointing the Kohanim and the Mishkan, placing blood on various parts of the Kohanim, and sequestering the Kohanim for the duration of it all. It was intense, and it was announced and performed quite publicly.

Viewed in isolation, the Milu'im could easily be understood as an important ritual, and nothing more. It was elaborate, it was grand, it took an entire week, but it was like any other inauguration or investiture. However, such a perspective is incorrect, for inasmuch as the Milu'im procedure was very technical, it was also designed to instill in the Kohanim an acute sense of devotion and kedushah (holiness).

In other words, the Milu'im procedure contained both an objective and a subjective component. Objectively, it endowed the Kohanim with Kedushas Kehunah (Sanctity of the Priesthood) and licensed them to perform Avodah. These are both legal concepts. And subjectively, the Milu'im procedure, with its drama, solemnity, uniqueness and strictures, inspired the Kohanim and infused them with an aura of sanctity, zeal and deveikus (closeness to Hashem).

This is why the parshah first features the tasks of Kohanim that pertain to korbonos, and it then features the Milu'im, for it was necessary that the Kohanim first be presented with the weighty and sacred responsibility and particulars of their role in Avodah (Sacrificial Service), so that they would profoundly appreciate and internalize the elevated import of it all and they would rise to the sacred charge. Only after vividly apprehending the special and holy character of Avodah and why it was such a privilege and an awesome responsibility could the Kohanim's investiture appropriately impact on them spiritually and emotionally. This is why it was necessary for Parshas Tzav to first present the korbonos and only then to feature the Milu'im.

This message may be expanded, for although halachic observance is a legal and technical requirement, it should not and cannot be done with a sterile feeling. When fulfilling mitzvos, we must look deeper and realize that we are performing the Will of the Supreme King, who chose us with love, brought us near to Him and intimately charged us with holy tasks. If one takes a step back and ponders the immensely powerful message of each mitzvah and the general significance of the mitzvos, his Torah observance will be radically enhanced. 

We find that gedolei ha-dor, the greatest Torah scholars throughout the ages, who plumbed the abstractions of Halacha and excelled in mastering its logos, were at the same time emotionally charged in an exceptional manner when performing mitzvos. It is our mandate to follow this example - an example that can be traced all the way back to Aharon and his sons at their investiture in Parshas Tzav.