Parashas Metzora · Passuk 15:11
Chabad.org — English translation + Rashi
Torah Temima points to Toras Kohanim.
English: “And his hands he did not rinse” — like his hands: just as his hands are in the visible [parts], so everything [requires immersion] in the visible — excluding hidden places that do not require immersion.
Visible limbs for immersion
Chazal limit the immersion requirement to exposed parts of the body; beis haseetarim need not be immersed.