John Calvin Commentary Leviticus 11:43

"Ye shall not make yourselves abominable with any creeping thing that creepeth, neither shall ye make yourselves unclean with them, that ye should be defiled thereby." — Leviticus 11:43 (ASV)

You shall not make yourselves abominable. He does not invite them to take care of their health, nor warn them of the danger of contracting diseases, but bids them beware of defiling themselves.

And a clearer explanation is provided: For I am the Lord your God: you shall therefore sanctify yourselves, for I am holy. So that they would not imagine that the main part of religion consisted in external ceremonies, they were to consider the nature of God. Since He is a Spirit, He is to be worshipped only spiritually.

Thus, holiness is only connected instrumentally with the distinction of foods, since their abstinence had no other object than that they should consecrate themselves to God. Therefore, the superstition of the Jews was inexcusable when they satisfied themselves with trifling observances,⁴⁷ as if one were to learn the letters of the alphabet without applying them to their use and reading what is written.

From their example, we perceive how eagerly people grasp everything they can to sustain themselves in their hypocrisy. For they not only twisted to their earthly notions the things that were profitable in the pursuit of true integrity of heart, but, not content with this, they heaped upon themselves many rites beyond what was required.⁴⁸ Hence, the water of expiation or lustration was always in use, even when they were unconscious of any pollution; hence also their anxious labor in washing cups and platters, so that it would readily appear how constantly human perversity abuses what God has appointed for the best of reasons.

⁴⁷ “Quand ils se sont arrestez a l’observation une et simple de choses frivoles; comme si quelqu’un apprenoit 1’ a, b, c, et qu’il ne luy chalust puis apres d’accoupler les lettres pour lire;” when they stopped at the bare and simple observation of frivolous things; as if one should learn the a, b, c, and cared not afterwards to join the letters together so as to read.—;” when they stopped at the bare and simple observation of frivolous things; as if one should learn the a, b, c, and cared not afterwards to join the letters together so as to read.—Fr..

⁴⁸ Addition in Fr., “Comme si la religion eust este enclose en choses de neant;” as if religion had been comprised in things of nought.;” as if religion had been comprised in things of nought.