The Ben Ish Chai (Rabbi Yosef Chayim of Baghdad, 1833-1909), in Parashat Nitzavim, discusses the widespread custom that men immerse in a Mikveh on Erev Rosh Hashanah in order to be Tahor (ritually pure) on the Day of Judgment. Immersion before Rosh Hashanah is particularly important for men with Tum'at Keri (the status of ritual impurity that results from a semenal emission). The Ben Ish Chai adds that before immersing in a Mikveh, a man must ensure to comb any knots in his hair and remove all traces of dirt from his entire body, including under the fingernails. In order for the immersion to be effective in eliminating Tum'a, no substance may come in between the body and the water. Just as a woman must untangle the knots in her hair and thoroughly cleanse herself before immersing to rid herself of her Nidda status, so must men undergo this process before immersing on Erev Rosh Hashanah.
However, Chacham Ovadia Yosef, in his work Halichot Olam, claims that the Ben Ish Chai's ruling is overly stringent. Halacha follows the view that one may pray and study Torah in a state of ritual impurity, and it is only a "Midat Chasidut" an additional level of piety to immerse before prayer or study. Therefore, since this immersion is altogether on the level of "Midat Chasidut," a man is not required to prepare his body for immersion on Erev Rosh Hashanah as a woman must upon completing her Nidda period. Thus, one need not remove his contact lenses or untangle his knots before immersing on Erev Rosh Hashanah.
What is the deeper meaning behind this practice of immersing on Erev Rosh Hashanah?
A human being originates in the mother's womb, where he is surrounded on all sides by water. (As we know, one of the stages of childbirth is the "breaking of the water," when the water surrounding the fetus exists the woman's body to allow for the child's delivery.) Immersing in a Mikveh likely serves as a reenactment, of sorts, of man's initial emergence into the world. As part of the process of Teshuva (repentance), a person returns to the water, to his origin and source, to the initial state of pristine purity in which he was first created, representing his efforts to spiritually cleanse himself and become pure like he had been at birth.
This symbolism takes on even greater significance on the festival of Rosh Hashanah, which we describe in our liturgy as "Harat Olam" the day of the world's creation. In truth, the world came into existence one week earlier, on the 25th day of Elul. Rosh Hashanah marks the day when man was created, and it is therefore appropriate as part of the commemoration of man's emergence to immerse in a Mikveh, symbolizing our efforts to return to our roots and our initial state of purity through the process of Teshuva.
Summary: It is proper for a man to immerse in a Mikveh on Erev Rosh Hashanah, which symbolizes the emergence of the human being from the womb in a state of pristine purity. Before this immersion, a man is not required to undergo the thorough process of cleaning his body and removing foreign substances such as contact lenses, as is required of a woman who immerses to divest herself of her Nidda status.
