Halakhah su Levitico 9:78

During Temple times, Birkat Kohanim would take place after the daily sacrificial offerings were completed. The Torah recounts that on the eighth day of the Mishkan’s dedication, the day that the kohanim were inaugurated in their service: “Aharon lifted his hands toward the people and blessed them. He then descended from [the altar where he] had prepared sin offering, burnt offering, and peace offering” (Vayikra 9:22). It is from here that we derive that Birkat Kohanim (also called “Nesi’at Kapayim” – “the lifting of the hands” – after this verse) took place at the conclusion of the sacrificial offerings. The reason for this is that after offering the sacrifices, which express our willingness to surrender and sacrifice ourselves for God, we are worthy of receiving His blessing.

To not shave the hair of the scab: To not shave the hair of the scab (netek), as it is stated (Leviticus 13:33), "but the scab, he shall not shave" - meaning to say that hair that is on the place of the scab, he shall not shave. And the language of Sifra, Tazria, Parashat Nega'im, Chapter 9:7 is "From where [do I know] that one who detaches the signs of impurity from within his scab, that he violates a negative commandment? As it is stated, 'but the scab, he shall not shave.'" And the matter is that the priest recognize the signs of impurity in the hairs.