Daf Yomi - Yoma 88 - Being Seen in the Azarah on Yom Kippur

The Rosh brings from Rabbeinu Sadya Gaon that after immersing on Erev Yom Kippur, one should recite a blessing. The Rosh disagrees and maintains that there is no blessing because there is no obligation. The Rosh explains that it is at most a custom and on customs we do not recite blessings. He brings a proof from the mitzva of taking the arovos on Sukkos which the Gemora explicitly states that no blessing is recited for it is only a custom from the prophets. He continues that perhaps one might say that there should be a blessing based on the words of Rabbi Yitzchak (R"H 16) that a person is obligated to purify himself before a Yom tov. He responds that this means purified from tumas meis which entails the sprinkling from the ashes of the parah adumah and this we do not have anymore.

It is evident from the Rosh that the mitzva of purifying oneself before the regel applies to Yom Kippur as well. It would appear that the Rambam disagrees with this. The Rambam in Tumas Ochlin (16:10) states that the reason one is obligated to purify himself before the Yom Tov is to be prepared to eat kodoshim and to enter the Beis Hamikdosh. This would not apply by Yom Kippur, for one doesn't eat kodoshim and there is no obligation to enter the Beis Hamikdosh, like there is by the other Yomim Tovim.