Комментарий о цитате к Бамидбар 18:6

'ויאמר ה' אל אהרן: אתה ובניך וגו, however no non-priest must approach (verse 4) if he does deliberately he will be executed as spelled out in verse 6. The nature of the penalty was sufficient to enforce this rule henceforth

Maimonides in the third part of his Moreh Nevuchim, chapter 49 writes that the reason for the עריות legislation is to reduce the frequency men indulge in cohabitation, to train people to accept that the sex act per se is considered revolting and that when it comes to the Torah’s prohibiting man’s pairing with the females of the species mentioned in our chapter, the common denominator found here is that the women in question are constantly part of his immediate environment and therefore represent a temptation due to their easy availability. Seeing that man is surrounded by such temptation, the Torah decreed harsh penalties against the violation of this legislation. Ibn Ezra in verse 6 cites similar reasons as governing this legislation.

For assistance. Meaning for the holy service, but not for mundane work. Rashi’s proof is from that which is mentioned in Parshas Korach, “that I have given you a gift to perform the work of the Tent of Meeting” (Bamidbar 18:6). From there one may infer that it was specifically for holy service, but not for the mundane.