but he shall not go through the veil or approach the altar, because he has a blemish, that he may not profane my sanctuaries, for I am the LORD who sanctifies them.”
The priesthood being confined to one particular family, and entailed upon all the male issue of that family throughout their generations, it was very likely that some or other in after-ages that were born to the priesthood would have natural blemishes and deformities: the honour of the priesthood would not secure them from any of those calamities which are common to men.
Commenting on Leviticus 21:16-24
And Moses told it to Aaron, and to his sons,.... What God had said to him concerning the priests defiling themselves for the dead, both common priests and high priest, and concerning their marriages and their blemishes; that they might be careful not to transgress the laws and rules given them concerning those things: and to all the children of Israel; to the heads of...
Only he shall not go in unto the vail, nor come nigh unto the altar, because he hath a blemish; that he profane not my sanctuaries: for I the LORD do sanctify them. (s) Into the sanctuary.