and to make a distinction and recognize a difference between the holy (sacred) and the common (profane), and between the [ceremonially] unclean and the clean;

Therefore, thus says the Lord [to Jeremiah],
“If you repent [and give up this mistaken attitude of despair and self-pity], then I will restore you [to a state of inner peace]
So that you may stand before Me [as My obedient representative];
And if you separate the precious from the worthless [examining yourself and cleansing your heart from unwarranted doubt concerning My faithfulness],
You will become My spokesman.
Let the people turn to you [and learn to value My values]—
But you, you must not turn to them [with regard for their idolatry and wickedness].

The priests shall teach My people the difference between the holy and the common, and teach them to distinguish between the (ceremonially) unclean and the clean.

When it is unclean, and when it is clean

“Be careful during an outbreak of leprosy, that you diligently observe and do according to all that the Levitical priests teach you; just as I have commanded them, so you shall be careful to do.

General references

This is the law for the one in whom there is an infection of leprosy, whose means are limited for his [ceremonial] cleansing.”

This is the law for the one who has a discharge and for the one who has a seminal emission, so that he is unclean by it;

These are the statutes which the Lord commanded Moses, between a man and his wife, and between a father and his daughter while she is a youth in her father’s house.