The following commentary covers Chapters 11 and 12.
the service and duty of the priests
established, there comes the discernment between holy
things and profane, and the judgment of defilements (chaps.
11-15), and what was to be done for the purification of
defiled persons. We see that it is this nearness of
separation unto God which alone can discern thus, and
such is the service and ever the duty of priests.
what was clean in food
First, as to food, that
which is allowed to be eaten. In general the principle
seems to be, that anything is allowed that is clean, in
this sense, first, that it is thoroughly according to its
element, that is, in principle, divine order (of course
here presented in a figure), as fishes having scales;
secondly, that was allowed which united mature digestion
to the absence of that wilful energy which goes boldly
through everything. These two qualities must be united.
The grossness which swallows down things as they are, or
the lack of quiet firmness, rendered unclean. To be clean,
it must be that which at the same time chews the cud and
divides the hoof. Of birds, the carnivorous night birds
and those which cannot be tamed are forbidden; creeping
things also, whatever grovelled and trailed itself on the
earth. In general, there was to be in their eating the
discernment of what was clean.
God's judgment on
what, as now connected with sin, is unclean
Then we have the judgment
of God fallen on that which would have been, for unfallen
man, joy and blessing. The birth of a man, connected now
with sin, renders unclean; that of a woman, in whom was
the transgression, being deceived, still more so .
 Connected with
this was the weakness of fallen nature (compare Gen. 1: 2).
All that belonged even to weakness of nature, being the
effect of sin, rendered unclean under the law. This is
also true spiritually. All this was the result of some
manifestation or other of the life that was in the flesh.
It was so with the leper; raw flesh rendered unclean, as
well as any other case where this life (which had become
unclean, and had been as set aside and under judgment
through sin), manifested itself externally, even though
weakness alone were the cause of its manifestation.