In the times of the Bet Ha’mikdash, there was an obligation to purify oneself before Yom Tob by immersing in a Mikveh. As people were required to visit the Bet Ha’mikdash and bring sacrifices on Yom Tob, they had to immerse in advance of Yom Tob in order to be pure. Nowadays, however, there is no strict Halachic requirement to immerse before Yom Tob. As we do not have the ashes of the Para Aduma with which to remove our status of Tum’at Met (ritual impurity resulting from contact with a human corpse), we remain Tameh even after immersing in a Mikveh. Hence, we cannot completely purify ourselves, and thus there is no obligation to immerse before Yom Tob.
Nevertheless, it is clear that immersing raises one’s level of sanctity and purity, and therefore it is appropriate for those who can to immerse in a Mikveh on Ereb Yom Tob in order to spiritually prepare themselves for the holiday. Nowadays, Baruch Hashem, we have many Mikva’ot available and immersing is not difficult. It would therefore be appropriate for those who can to make a point of immersing on Ereb Yom Tob, so they can go into the holiday in a higher state of purity and Kedusha.
