Siman 88

The Rambam wrote at the end of the laws of Kiryat Shema: All those who are impure are obligated in Kiryat Shema and recite the blessings before it and after it, and they remain in their impurity even though it is possible for them to emerge from their impurity on that very day, such as those who touch a sheretz, or a niddah, or a zavah, and the like. Ezra and his beit din enacted that a ba'al keri alone should not read words of Torah, and they excluded him from the general rule of other impure people until he immerses. This enactment did not spread throughout all of Israel, and the majority of the community did not have the strength to abide by it; therefore, it was nullified. All of Israel have already adopted the custom to read from the Torah and to recite Kiryat Shema while they are ba'alei keryin, because words of Torah do not receive impurity, as it is said: "Is not My word like fire? says the Lord" – just as fire does not receive impurity, so too a word of Torah does not receive impurity. Thus far his words.

And the reason that Ezra enacted immersion for ba’alei keri is because it stems from lightheadedness (Tur). And furthermore: so that Torah scholars should not be found with their wives like roosters (Gemara 22a). And from the words of the Rambam, it appears that it was not the sages who abolished it, but rather it was abolished on its own, because they could not withstand this enactment. And so it is implied from the language of the Gemara there, which says: the world practiced... And even though it says there "they abolished the immersion," one can say that after they practiced thus, the sages strengthened this matter. And therefore we find in the Mishnayot that they practiced this enactment, because it had not yet been abolished. And even now there are those who are meticulous who observe to immerse for their keri, and this is not like one who violates an enactment of the sages who commanded to abolish it. For in truth, the sages did not decree to abolish it, but rather the people themselves practiced thus and the enactment spread, and the sages agreed to this because of the neglect of Torah and because of the neglect of procreation. Therefore, even now they can be stringent regarding this immersion, provided that because of this he does not pass the time for Keriat Shema or prayer with a tzibbur. And the Rambam in a responsum testified about himself that in all his days he never neglected this immersion.

Our teachers, the authors of the Tosafot, wrote there that some explain that they only abolished it for Torah but not for prayer. And the Ri explained that there is no difference, see there. And so wrote the Rambam and the Rosh and all the poskim. And there are some of the Geonim who said that although they abolished the immersion, nevertheless, washing with nine kabin is required. And our teachers, the poskim, disagreed with this, as the Tur wrote that he requires neither immersion nor washing with nine kabin. And this immersion is even in drawn water, as it is stated in the eighth chapter of Mikvaot. And even according to the enactment of Ezra, it is only for a complete seminal emission that discharges like an arrow. But if one saw "divided water" – he does not require immersion even according to the enactment (Magen Avraham, subsection 1). And nine kabin is specifically from three vessels, no more. And he should not pause from the pouring of the first until he begins with the second, and likewise from the second to the third (Taz, subsection 1).

Our teacher, the Rema, wrote: There are those who wrote that a woman who is a niddah should not enter the beit knesset during the days of her seeing, or pray, or mention the Name, or touch a book. And there are those who say she is permitted in everything, and such is the primary ruling. However, the custom in these lands is like the first opinion, and during the days of whitening they practiced permissiveness. And even in a place where they practiced stringency, nevertheless, on the Yamim Noraim and the like, when many gather to go to the beit knesset – they are permitted to go to the beit knesset like other women, for it is a great sadness for them that everyone gathers and they would stand outside. Thus far his words. And from the first day of Selichot is called "Yamim Noraim" (Magen Avraham, subsection 3). And when they go, they may also pray. And so too after childbirth, when women practiced going to the beit knesset, or at the time of the marriage of her son or daughter – they may go and pray (ibid.). And even during the days of her niddah, she is obligated to recite Birkat HaMazon, for they are obligated by Torah law, provided they are clean from blood and from filth (see there in the Magen Avraham). And she should not gaze at the Sefer Torah at the time of Hagbahah (Taz).