Exodus 29:33

And they shall eat those things wherewith the atonement was
made
For the sins of Aaron and his sons, for they were men of infirmity, and needed sacrifice for sin themselves; and herein Christ their antitype excelled them, that he had no sin of his own, and needed not to offer first for them, and then for the sins of others, as Aaron and his sons, the types of him, did; and their eating of the sacrifice for atonement points at the receiving of the atonement of Christ's sacrifice by faith, and the enjoyment of it and the blessings following on it:

to consecrate and to sanctify them;
that they might be filled and fitted, and set apart and devoted to the office of the priesthood, and minister in it:

but a stranger shall not eat [thereof], because they are holy;
meaning not one of another nation, but of another family, though an Israelite; the Targum of Jonathan renders it, a profane and common person, a layman, one that was not a priest; who, though he was of the seed of Israel, yet not being of the seed of Aaron, as Aben Ezra interprets it, he might not eat of the above things, because they were devoted to holy uses; and therefore none but such who were sanctified or set apart to sacred service might partake of them.