Halakhah for Zevachim 40:17

ת"ש פרה רבי חייא ברבי יוסף אמר מקדש בכלי שרת בפנים ויוצא ורבי יוחנן אמר אפילו בחוץ ואפילו בכלי חול ואפילו במקידה של חרס

but if his whole body went out, you may [certainly] be in doubt. Said R'Zebid to R'Papa. Come and hear: If [the priest] went without the barrier of the wall of the Temple court, if [it was his intention] to tarry there, he needs immersion; if for a short while, he needs sanctification of hands and feet! - Said he to him: That means where he went out to ease himself at nature's call. But that is explicitly taught: He who eases himself needs immersion, and he who answers nature's call requires sanctification of hands and feet? - He [first] teaches [the general law] and then defines it.<span class="x" onmousemove="('comment',' The Tanna first states the law about going out, and then defines the cases to which this law applies.');">¹³</span> Come and hear: [For the services in connection with the red] heifer, R'Hiyya B'Joseph said: [The priest] must sanctify [himself] from a service vessel within and then go out;<span class="x" onmousemove="('comment',' The burning of the red heifer and the gathering of its ashes and mixing it with water, which are the services here referred to, were done outside Jerusalem.');">¹⁴</span> whereas R'Johanan maintained: [He can sanctify himself] even without [the Temple], even in a profane vessel, even in a fire pot! - Said R'Papa. The [red] heifer is different; since all its services are without, going out does not disqualify it. If so, why must he sanctify [himself at all]? - We want it to be done like the services within. It was asked: Is uncleanness effective in respect of sanctification of hands and feet?<span class="x" onmousemove="('comment',' It is now assumed that the question is: if the priest's hands became unclean, without the rest of his body, must he resanctify them?');">¹⁵</span> If you say that going out does not invalidate [sanctification], that may be because the person remains fit; but here that the person is no longer fit [for service] he turns his mind from it.<span class="x" onmousemove="('comment',' Which nullifies sanctification.');">¹⁶</span> Or perhaps, since he will be fit again, he is careful and does not turn his mind away from it? - Come and hear: If [the priest] sanctified his hands and his feet and they became unclean, he must immerse them, but need not [re-]sanctify them! - Where his hands [only] became unclean, we do not ask; our question is where his whole body was defiled.' His whole body'! surely I may deduce that he will turn his mind away from it, since he must wait for the setting of the sun?<span class="x" onmousemove="('comment',' He does not become clean even after immersion until sunset.');">¹⁷</span> - [The question arises where] e.g. he became unclean just before sunset! Come and hear: [For the service in connection with the red] heifer, R'Hiyya B'Joseph said: [The Priest] must sanctify [himself] from a service vessel within and then go out; whereas R'Johanan maintained: [He can sanctify himself] even without the Temple, even in a profane vessel, even in a firepot.

Sefer HaChinukh