4,018. Visible vs. Invisible Blemishes

Hilchos Bias HaMikdash 6:6

If a kohein with a blemish in category 1 (the kind that disqualifies a kohein from serving and an animal from being offered) serves, intentionally or unintentionally, the service is invalid; if he did so intentionally, he is subject to the penalty of lashes. If a kohein with a blemish in category 2 (the kind that only disqualifies a kohein from serving) serves, the service is valid even though he is subject to lashes. If he has a blemish in category 3 (the kind that disqualifies him Rabbinically for appearances’ sake), the service is valid and he is not subject to lashes.

Hilchos Bias HaMikdash 6:7

Only visible blemishes disqualify a kohein from serving. If a blemish is internal, such as if his kidney or spleen was removed or his intestine was punctured, the kohein’s service is valid even though he is a “treifah” (i.e., the blemish will ultimately result in his death). The examples of a broken leg and a broken arm given in Leviticus 21:19 are visible, so we infer that all disqualifying blemishes must be visible.