Responsa for Niddah 31:46

דיה בשני עדים כל הלילה:

when the time of her regular period arrived and she did not examine herself, she is nevertheless clean, because fear suspends the menstrual flow.<span class="x" onmousemove="('comment',' Infra 39a. ');">⁴⁰</span> The reason then<span class="x" onmousemove="('comment',' Why she is regarded as clean. ');">⁴¹</span> is that there was fear, but if there had been no fear she would have been deemed unclean. Thus it clearly follows [that the necessity for an examination at] regular periods is Pentateuchal. May it be assumed that the following Tannas also differ on the same principle? For it was taught: If a woman observed some blood [that might be] due to a wound,<span class="x" onmousemove="('comment',' In her womb. ');">⁴²</span> even if this occurred during her usual period of menstruation, she is deemed to be clean;<span class="x" onmousemove="('comment',' The blood being attributed to the wound. ');">⁴³</span> so R. Simeon b. Gamaliel. Rabbi ruled: If she has a regular period<span class="x" onmousemove="('comment',' If she has no regular period Rabbi, for the reason given in prev. n., agrees with R. Simeon b. Gamaliel. ');">⁴⁴</span> she<span class="x" onmousemove="('comment',' If the blood was observed on the day the period was due to commence. ');">⁴⁵</span> must take her period into consideration.<span class="x" onmousemove="('comment',' Sc. she is regarded as unclean, since it is possible that some particle of menstrual blood was mixed up with that of the wound. ');">⁴⁶</span> Now do they not differ on this principle, one Master<span class="x" onmousemove="('comment',' Rabbi. ');">⁴⁷</span> holding that [the examinations at] the regular periods are Pentateuchal, while the other Master<span class="x" onmousemove="('comment',' R. Simeon b. Gamaliel. ');">⁴⁸</span> holds that they are only Rabbinical? — Rabina replied: No; both may agree that [the examinations at] the regular periods are only Rabbinical, but it is on the question whether the interior of the uterus is unclean<span class="x" onmousemove="('comment',' Lit. 'as to the source, the place thereof is unclean'. And, therefore, capable of imparting uncleanness to any clean blood that passes through it. ');">⁴⁹</span> that they differ. R. Simeon b. Gamaliel holds that the woman is clean<span class="x" onmousemove="('comment',' Sc. she is not subject to the major uncleanness of menstruation which extends over seven days. ');">⁵⁰</span> but the blood<span class="x" onmousemove="('comment',' Though coming from a wound. ');">⁵¹</span> is unclean because it comes through the uterus,<span class="x" onmousemove="('comment',' Where it contracts an uncleanness (a 'father of uncleanness') which causes it to impart a one day's uncleanness to a human being, so that any object touched by the woman on that day becomes unclean. ');">⁵²</span> and Rabbi<span class="x" onmousemove="('comment',' Relaxing the law. ');">⁵³</span> in effect said to him: If<span class="x" onmousemove="('comment',' By regarding the blood as unclean. ');">⁵⁴</span> you take into consideration the possibility of her usual menstrual flow, the woman also should be unclean,<span class="x" onmousemove="('comment',' For seven days, as any other menstruant. ');">⁵⁵</span> and if<span class="x" onmousemove="('comment',' Since you exempt the woman from menstrual uncleanness. ');">⁵⁶</span> you do not take into consideration the possibility of her usual menstrual flow, [the blood also should be clean since] the interior of the uterus<span class="x" onmousemove="('comment',' Lit., 'the source of its place'. ');">⁵⁷</span> is clean. <b><i>MISHNAH</i></b>. BETH SHAMMAI RULED: A WOMAN NEEDS TWO<span class="x" onmousemove="('comment',' Previously unused. ');">⁵⁸</span> TESTING-RAGS FOR EVERY INTERCOURSE,<span class="x" onmousemove="('comment',' One is used before, and the other after and both are preserved until the morning when they are to be examined in daylight. ');">⁵⁹</span> OR SHE MUST PERFORM IT IN THE LIGHT OF A LAMP.<span class="x" onmousemove="('comment',' So that the testing-rag may be immediately examined. ');">⁶⁰</span> BETH HILLEL RULED: TWO TESTING-RAGS<span class="x" onmousemove="('comment',' One of which is used prior to the first intercourse and the other after the last. ');">⁶¹</span> SUFFICE HER FOR THE WHOLE NIGHT.<span class="x" onmousemove="('comment',' This being sufficient to determine whether she is menstrually unclean and whether she is to convey uncleanness to any clean object she may have handled. (So Rashi; cf., however, Tosaf. and Tosaf. Asheri for a different interpretation.) ');">⁶²</span>

Teshuvot Maharam