וּֽלֲהַבְדִּ֔יל בֵּ֥ין הַקֹּ֖דֶשׁ וּבֵ֣ין הַחֹ֑ל וּבֵ֥ין הַטָּמֵ֖א וּבֵ֥ין הַטָּהֽוֹר׃
그리하여야 너희가 거룩하고 속된 것을 분별하며 부정하고 정한 것을 분별하고
Ramban
AND THE ETERNAL SPOKE UNTO MOSES AND TO AARON, SAYING UNTO THEM: 2. SPEAK UNTO THE CHILDREN OF ISRAEL. The commandments [mentioned] in these sections apply to both Israelites and the priests, but their subject-matter affects mostly the priests, for they must always guard themselves from touching impure objects, since they have to come into the Sanctuary and eat the hallowed food [which they may not do when they are impure]. Moreover, when an Israelite errs in these matters, he has to bring an offering [to effect atonement for his transgression],149See Ramban above, 5:2. which the priests offer up. Furthermore, He commanded them, And that ye may put difference between the holy and the common, and between the unclean and the clean;150Above, 10:10. It should be noted at this point that the terms “clean” or “cleanness,” and “unclean” or “uncleanness,” are here in the translation used interchangeably with those of “pure” or “purity” and “impure” or “impurity”. This was felt necessary in order to convey the thought that uncleanness in the Biblical sense is not something that can be rubbed off with some material object. On the other hand, the terms “pure” and “impure” suggest a far greater measure of spirituality. The same comment applies equally to the following portions of the Torah — Tazria, Metzora, etc. thus they must instruct Israel concerning the impure and the pure so that they can be careful of them. It was for this reason that the communication about these laws came to both Moses and Aaron, or to Moses to say to Aaron, commanding both of them, speak unto the children of Israel, and this is the reason why these laws were said in the Book of the Laws of the Priests [i.e., this Book of Leviticus]. In this section He also warns against eating impure foods, so as not to defile the Tabernacle and its hallowed things.
Sforno
ויאמר ה' אל משה אמור אל הכהנים, what has been written earlier so that they will understand and instruct each other in the various categories of ritual impurities and contaminations, including the difference between ritually pure domestic beasts and birds, for these are the aspects of foremost concern to the priests on a regular basis as we read in 10,10-11 ולהבדיל בין הקדש ובין החול, ובין הטמא ובין הטהור ולהורות, “and to separate the sacred from the profane, and the ritually impure, and between the ritually contaminated, and to teach these values.”
Kli Yakar
When a person has on the skin of his flesh, etc. The section on skin afflictions [nega’im] is juxtaposed to the previous section that discusses circumcision, to teach you that circumcision pushes off skin afflictions, because in every place, the earlier commandment pushes off the later one, as explained above in Parashat Vayakhel regarding the statement of our Sages that the Sabbath precedes the Tabernacle, telling you that the Sabbath pushes off the work of the Tabernacle. And by way of allusion, it seems to me that this relates to our Sages’ statement (Nedarim 31b): “Great is circumcision, for it pushes off skin afflictions.” This is because circumcision is generally a catalyst for the removal of all four types of “foreskins,” including the “foreskin of the lips,” and when one is circumcised from the foreskin of the lips, they will not speak evil speech [lashon hara], and thus will not come to have skin afflictions, which come as a result of evil speech (Arachin 15b). Regarding this, Moses complained, saying: From when [az] I came to speak in Your name, etc. (Exodus 5:23) according to the Midrash (Yalkut Shimoni, Exodus 174) that states that all of Moses’ transactions were with az [the Hebrew word for “when/then”], alluding to circumcision. This is also explicitly concluded in the Yalkut Parashat Beshalach (241:15) on the verse Then [Az] Moses sang: that the sea was split in the merit of circumcision, which is performed on the eighth day, corresponding to the numerical value of az [which is eight]. Similarly, all those instances of az mentioned in Midrash Devarim Rabbah on the verse Then [Az] Moses set apart (Deuteronomy 4:41) also allude to circumcision, which saves one from bloodshed, as explained above in Parashat Bo on the verse See that evil is before your faces (Exodus 10:10). Likewise, the salvation of his [Moses’] life was only through az, as it says: Then [Az] she said, “A bridegroom of blood because of the circumcision” (Exodus 4:26). And similarly, his complaint was only with az, as it says: From when I came to Pharaoh to speak in Your name (Exodus 6:23). Moses said: “I know that I am of uncircumcised lips, and I only came to speak in Your name from az, as I relied on circumcision, which is alluded to in az, that it would also be a catalyst for fixing the foreskin of the lips, but I see that it has not helped at all.”