Chapter 9, Mishnah 4 includes four teachings unrelated to Shabbos, but seeking Scriptural support, like the other mishnahs in this chapter. The first is that a wife is rendered tamei if she discharges semen within three days after having relations with her husband. The decree relates to Moses’ command that the people restrain themselves from relations for three days before the giving of Torah at Mount Sinai. Question is how we measure the days. Rabbis Elazar ben Azaryah, Yishmael, Yosei, and Akiva have conflicting opinions. Rambam would ultimately rule three 12-hour periods. In passing, we also learn that couples are obligated to have relations in the dark, or at least under cover. Rabbi Manis Friedman teaches that this law does wonders for preserving romantic mystery and intimacy. The other decrees in the mishnah relate to washing a recently circumcised baby on Shabbos, the scarlet thread between the horns of the Yom Kippur scapegoat and the prohibition on anointing oneself with oil on Yom Kippur.