John Calvin Commentary Leviticus 5:2

"Or if any one touch any unclean thing, whether it be the carcass of an unclean beast, or the carcass of unclean cattle, or the carcass of unclean creeping things, and it be hidden from him, and he be unclean, then he shall be guilty." — Leviticus 5:2 (ASV)

Or if a soul touch any unclean thing. This precept seems not only to be superfluous but also absurd; for Moses had already shown sufficiently how uncleanness contracted by touching a dead body, or any other unclean thing, was to be purified, and had prescribed an easy and inexpensive mode of purification. This repetition appears, therefore, to be useless.

But to impose a heavier punishment on an offense that is excused by a claim of error, rather than on one where error is not mentioned, seems unjust.

However, we must remember that not only is the uncleanness itself punished here, but also the inadvertence that caused the polluted person to omit the purification.

For it may be that those who thus remain sluggish in their sins pollute for a time the service of God. No wonder, then, that a heavier punishment is inflicted where error, springing from negligent and blatant complacency, produces even more sins, so that believers may be stirred to greater watchfulness.

Let the reader, therefore, recall that the offense now referred to did not consist in the mere touching of a dead body, but in the thoughtlessness itself. For if all would diligently meditate on the Law of God, forgetfulness would not so easily steal over them, through which the distinction between right and wrong is lost.

The same is the reason for the following ordinance, where Moses subjects to the same punishment anyone who touches an unclean or defiled man; thus, the very contact of a woman at a particular period produces pollution.