וְאַתָּ֣ה וּבָנֶ֣יךָ אִ֠תְּךָ תִּשְׁמְר֨וּ אֶת־כְּהֻנַּתְכֶ֜ם לְכָל־דְּבַ֧ר הַמִּזְבֵּ֛חַ וּלְמִבֵּ֥ית לַפָּרֹ֖כֶת וַעֲבַדְתֶּ֑ם עֲבֹדַ֣ת מַתָּנָ֗ה אֶתֵּן֙ אֶת־כְּהֻנַּתְכֶ֔ם וְהַזָּ֥ר הַקָּרֵ֖ב יוּמָֽת׃ (ס)
Ikaw at ang iyong mga anak na kasama mo ang mangangalaga sa inyong pagkasaserdote, para sa lahat ng may kinalaman sa altar at sa nasa loob ng tabing, at kayo ang maglilingkod. Bilang paglilingkod na kaloob ay ibinibigay Ko sa inyo ang inyong pagkasaserdote; at ang sinumang hindi kabilang sa inyo na lumapit ay papatayin.
Rashi
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].
Ramban
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).
Sforno
תשמרו את כהונתכם. To ensure that a non-priest, such as King Uzziah, does not enter the domain reserved exclusively for the priests.