While discussing the rules and regulations that relate to sensitivity in matters of a sexual nature, the Gemara relates the following story:
The Sage in the school of Eliyahu taught a baraita that deals with this halakha: There was an incident involving one student who studied much Mishna and read much Bible, and served Torah scholars extensively, studying Torah from them, and, nevertheless, died at half his days, half his life expectancy. His wife in her bitterness would take his phylacteries and go around with them to synagogues and study halls, and she said to the Sages: It is written in the Torah: “For it is your life and the length of your days” (Devarim 30:20). If so, my husband who studied much Mishna, and read much Bible, and served Torah scholars extensively, why did he die at half his days? Where is the length of days promised him in the verse? No one would respond to her at all.
Eliyahu said: One time I was a guest in her house, and she was relating that entire event with regard to the death of her husband. And I said to her: My daughter, during the period of your menstruation, how did he act toward you? She said to me: Heaven forbid, he did not touch me even with his little finger. And I asked her: In the days of your white garments, after the menstrual flow ended, and you were just counting clean days, how did he act toward you then? She said to me: He ate with me, and drank with me, and slept with me with bodily contact and, however, it did not enter his mind about something else, i.e., conjugal relations. And I said to her: Blessed is the Omnipresent who killed him for this sin, as your husband did not show respect to the Torah. The Torah said: “And to a woman in the separation of her impurity you should not approach” (Vayikra 18:19), even mere affectionate contact is prohibited.
The early commentaries wondered how that student, who was a Torah scholar, could treat Torah matters with such disdain. By Torah law, a menstruating woman is impure until she immerses herself in a ritual bath. They explain that his custom or the prevailing custom (Tosafot) was that a woman would immerse herself at the end of the days of her menstrual flow, when her period of impurity ended by Torah law. As a result, during those extra days added due to the stringency that Jewish women imposed upon themselves (see the discussion of this stringency in Massekhet Nidda, daf, 66), he did not conduct himself with the same stringency (Ramban; Rashba).