One may wonder why Parshat Tetzave starts at the end of Perek כז, with the oil for the Menora, which was already mentioned in the beginning of Teruma (שמן למאור) it would probably make more sense to start at beginning of Chapter כח which starts with the process of appointing Aharon and creating the vestments of the בגדי כהונה.
If we take a careful look, we will realize the word ואתה appears three times at the beginning of the Parsha. ואתה תצוה, as well as ואתה הקרב אליך and ואתה תדבר את כל חכמי לב.
Hence, ואתה תצוה is of course an apt beginning.
Moshe himself is commanded to supervise the collection and manufacturing of the oil, induct Aharon and his children, and address to those responsible for building the Mishkan.
The Rishonim note this, with the Ramban explaining that since the process of making the שמן was complicated, Hashem wanted Moshe Rabbeinu to personally oversee it and make sure it was done properly.
The Netziv adds another level of explanation: We know that the שמן of the Menorah represents Torah (the Netziv gets very specific regarding this point, if anyone wants to look and see). Torah is called תורה אור . In the Mishkan, the Menorah was in the south, and he who wishes to gain wisdom turns to that direction.
הרוצה שיחכים ידרים.
Furthermore, the Gemara (Brachos 57) tells us that if someone dreams of שמן זית they should look forward to the מאור – the light of Torah. There are also many other connections between שמן and תורה, and of course, Moshe was the bearer, the teacher and to a large degree developed much of the Torah. This message is appropriate on 7 Adar, as we enter the Purim season, as Purim includes a recommitment to Torah acceptance קיימו וקיבלו. Likewise, In the Pasuk ליהודים הייתה אורה ושמחה וששון ויקר, the Gemara explains that the אורה refers to תורה .
Wishing you all אורה שמחה ששון ויקר
Shabbat Shalom
