Commentary for Numbers 18:7

עבדת מתנה [I HAVE GIVEN YOUR PRIESTHOOD UNTO YOU] AS A SERVICE OF GIFT — This means as a gift have I given it to you, [and the stranger that comes near shall die].

I GIVE YOU THE PRIESTHOOD AS A SERVICE OF GIFT. “[This means that] it shall be to you as a gift.” This is Rashi’s language, and his intention thereby is to state that it is given to you as a complete gift, [to such an extent] that [as the verse continues], a non-priest who draws near [to do the service] will be liable to be put to death [by the hand of Heaven]. The correct interpretation appears to me to be that He is saying: “and you shall perform the service of the priesthood, but it is not to be regarded by you as a burdensome task, like that imposed upon the servants of kings, but I have given you the service of a great gift through it, for glory and for splendor¹⁹⁷Ibid., 28:2. from Me.” This is similar to the interpretation of the Rabbis:¹⁹⁸Sotah 15a. “L’moshchah¹⁹⁹Further, Verse 8. — as a distinction, [so that gifts given to the priests from the offerings are to be eaten by them] in the way that kings eat.”²⁰⁰I.e., roasted in fire and eaten with mustard (Chullin 132b).

תשמרו את כהונתכם. To ensure that a non-priest, such as King Uzziah, does not enter the domain reserved exclusively for the priests.