“Your umbilicus is like a moon-shaped basin in which no mixed wine is lacking. Your stomach is like a heap of wheat, hedged about with roses” (Shir Hashirim 7:3)
The Midrash states (Shir Hashirim Rabbah 7:3) that the roses referred to in this pasuk are divrei Torah, fragile as roses… The natural order is that a man marries a woman at great expense. He wants to have relations with her, when she tells him, “I have seen the redness of the rose (the blood of niddah).” He immediately distances himself from her. What caused him to keep away from her? Is an iron wall erected between them? Is a metal bar separating them? Was he bitten by a snake or scorpion? It is the words of Torah, fragile as the rose, as the pasuk says (Vayikra 18:19), “You shall not approach a woman in her time of unclean separation.”
The Gemara relates (Sanhedrin 37a): A Sadducee once asked Rav Kahana, “You maintain that a woman who is a niddah may be secluded with her husband. Can cotton catch fire and not be singed?” Rav Kahana responded, “The Torah testified that we are a nation fenced in by roses. Even delicate roses are sufficient to keep us from making breaches in the Torah’s commands.”
David asked Hashem, “Am I not devout? All of the kings of the east and west sit on their royal thrones, while I am engaged in dirtying my hands with the blood of placentas and fetal membranes, all in order to help a woman become pure to her husband. Moreover, whenever I decide a ruling, I confer with Mefiboshet, my teacher. I ask, ‘Did I rule correctly?’ ‘Did I judge properly?’ ‘Did I grant merit accordingly?’ ‘Did I pronounce purity appropriately?’ ‘Did I pronounce defilement fittingly?’ and I was never ashamed” (Berachot 4a).
The Gemara asks (Niddah 31b) in the name of Rabbi Meir, “Why does the Torah command a niddah to wait seven days until she can become pure? In order that her husband should not become accustomed to her and eventually be disgusted with her. She maintains seven days of preparation for purity, so that she may be as cherished by her husband as when she stood under the chuppah.”
The Ramban states (Iggeret Hakodesh, pg. 323) that one should not consider marital relations as ugly or unseemly. Chalilah for one to think this way. Marital relations are called ידיעה, the same word used for lofty forms of knowledge. If this matter did not contain tremendous levels of sanctity, it would never be called by this name.
The Gemara relates (Shabbat 13a) the following tale: A Talmudic scholar who studied much Torah and served talmidei chachamim died at a very young age. His wife took his tefillin and visited the Batei Kenesiot and Batei Midrashot with the following grievance on her lips, “The Torah states that it is our life and the length of our days. My husband learned so much Torah and served talmidei chachamim. How could he have died so young?” No one had an answer for her.
One time, Eliyahu Hanavi visited her home. She related the incident of her husband’s passing. He replied, “My daughter, how did you and your husband observe your niddah period? Did he come near you?”
“Chas v’shalom,” was her immediate reply. “He did not even touch me with his little finger.”
“And what about your seven days of cleanliness before purification?” he pressed.
“During those days, we ate and drank together. We even slept in one bed, but nothing more.”
To which Eliyahu finally offered her an explanation for her husband’s untimely death. He said, “Blessed is He Who killed your husband and did not allow his Torah study to bribe Him. The Torah commands a man to maintain complete distance from his wife in her niddah state, until she immerses in a mikveh.”