All of Aharon’s sons became Kohanim in the original ordination, but his grandchildren, including Pinchas, didn’t. Why is this? Rashi says that Pinchas got in this parsha because he wasn’t ordained at the time when Aharon’s sons were, but he did get ordained later in this parsha.
Rav Schwab (in his book Ma’ayan Beis HaShoeivah) asks why he wasn’t ordained at the original time. Additionally, the blessing of the Kohanim says that Hashem sanctified the kohen with the holiness of Aharon, but in the case of Pinchas, he was sanctified separately so his descendants should say that Hashem sanctified them with the holiness of Pinchas and not Aharon.
Aharon’s priesthood was defected because he built the egel hazahav (golden calf). It went on only to his children, not his grandchildren or anyone else. When Pinchas killed Zimri, he was doing the exact opposite of Aharon: He killed an idolater and Aharon made an idol, so Pinchas automatically became a Kohen. Since he repaired the defect from Aharon, therefore Aharon’s holiness extended to Pinchas.
Much gratitude toward my brother, Ariel Weinreich, for providing and correcting this and many other divrei Torah.
PS: Yeah, I couldn’t really think of an idea for a picture, and the current one has little to do with the actual dvar Torah, so tell me if you have an idea for one relating to this dvar Torah. I’ll can change it!