[א] "ואם שכב ישכב" – לרבות שתי שכיבות. "ואם שכב ישכב" – לרבות למערה. "איש" – פרט לקטן. או יכול שאני מוציא בן ט' שנים ויום אחד? ת"ל "ואם שכב ישכב" 1) (Vayikra 15:24) ("And if a man lie, lie, with her, then her niddah state shall be upon him, and he shall be unclean for seven days; and every mishkav on which he lies shall be unclean.") "lie, lie": to include two manners of lying (i.e., natural coitus and unnatural [sodomy]). "And if lie, lie": to include peripheral (non consummated) contact. "a man": to exclude a minor. I might think to exclude one of nine years and a day (or older). It is, therefore, written "and if he lie, lie." (and one of that age comes within the context of "lying.")
[ב] "אותה" – פרט למצורעת. והלא דין הוא! מה הנדה שאינה מטמאה בביאה – מטמאה את בועלה, מצורעת שהיא מטמאה בביאה אינו דין שתטמא את בועלה?! ת"ל "אותה" – פרט למצורעת. 2) "with her" (a niddah): to exclude a woman leper (i.e., If one has coitus with her, her state of "leper" is not upon him.) (For without a verse) would it not follow a fortiori (that her state is upon him, viz.:) If a niddah, who does not confer tumah (upon all that is in a house), by entering it, does confer tumah upon one who cohabits with her, then a leprous woman, who does confer tumah by entry, how much more so should she confer tumah upon one who cohabits with her! It is, therefore, written "with her" (a niddah), to exclude a woman leper.
[ג] "ותהי נדתה עליו" – יכול יעלה לרגלה? ת"ל וטמא שבעת ימים". יאמר "וטמא שבעת ימים" ומה ת"ל "ותהי נדתה עליו"? יכול לא יטמא אדם וכלי חרש? ת"ל "ותהי נדתה עליו" – מה היא מטמא אדם וכלי חרש אף הוא יטמא אדם וכלי חרש. אי מה היא מטמאה משכב ומושב לטמא אדם ולטמא בגדים אף הוא יטמא משכב ומושב לטמא אדם ולטמא בגדים. ת"ל "ותהי נדתה עליו וטמא שבעת ימים וכל המשכב אשר ישכב עליו יטמא" – שאין ת"ל, אלא שנתקו הכתוב מטומאה חמורה והביאו לטומאה קלה שלא יטמא אלא אוכלין ומשקין. 3) "then her niddah state shall be upon him." I might think that he followed her schedule (e.g., if he cohabited with her on her third day, he completes another four days as she does, and immerses and becomes tahor); it is, therefore, written "and he shall be unclean for seven days" (even if he cohabited with her on her seventh day). Let it be written "and he shall be tamei seven days." Why "then her niddah state shall be upon him?" I might think that he does not confer tumah upon men and earthen vessels; it is, therefore, written "then her niddah state shall be upon him" — Just as she confers tumah upon men and earthen vessels, so does he. I might then think that just as she confers tumah upon a mishkav to confer tumah upon men and garments, so does he. It is, therefore, written "then her niddah state shall be upon him, and every mishkav on which he lies shall be unclean." Let this ("and every mishkav, etc.") not be written, (for we can learn this from "then her niddah state, etc.") Its purpose must be, then, to cut him off from stringent tumah (that his mishkav not be as stringent as hers, to confer tumah upon men and vessels upon it) and to bring him to lesser tumah, that (his mishkav) confer tumah only upon food and drink.
[ד] נמצאת אתה אומר משכבו כמגעו. מה מגעו לטמא אחד ולפסול אחד, אף משכבו לטמא אחד ולפסול אחד. 4) In sum, then, you are saying that his mishkav (that of a man who touches the mishkav of one who cohabited with a niddah) is like his touching him. Just as his touching him confers tumah upon one (himself) and invalidates one (thing, i.e., the terumah that he then touches), so, (touching) his mishkav confers tumah upon one and invalidates one.
[ה] נמצאת אתה אומר, ככר של תרומה שהיא כרוכה במפה ונתונה בין כר לחברו, אם כנגדו נתונה – טמאה, שאם נטמאה המפה נטמאה הככר. ושלא כנגדו – טהורה, שאין מגעו מטמא בגדים. 5) We find, then, that if a loaf of terumah were wrapped in a towel and placed between one mattress, (that which the cohabiter is lying on) and another — If it (the loaf) were aligned with him (the cohabiter), it becomes tamei. For if the towel becomes tamei (as the mishkav of the cohabiter), the loaf (within it) becomes tamei, [his mishkav conferring tumah upon food and drink]); and if it (the loaf) were not aligned with him, it is tahor, its touching (i.e., the touching of the towel by the mishkav) not conferring tumah upon garments, (in this instance, the towel).
[ו] "וטמא שבעת ימים" – שיספור שבעה לביאה אחרונה. הלא דין הוא! מיטמא במת ומיטמא בנדה. מה מצינו כשהוא מיטמא במת אינו סופר שבעה אלא לטומאה אחרונה, אף כשהוא מיטמא בנדה לא יספור שבעה אלא לביאה אחרונה. 6) "and he shall be tamei for seven days": He counts the seven from the last cohabitation. (Why is a verse needed for this?) Does it not follow by induction, viz.: He becomes tamei by a dead body and he becomes tamei by a niddah. Just as we find with the first that he counts seven days only from the last tumah, so when he becomes tamei by a niddah, he should count the seven days only from the last union.
או כלך לדרך זה: היא מיטמאה ומטמאה את בועלה. מה היא אינה סופרת שבעה אלא לראיה הראשונה אף כשהוא מיטמא בה לא יספור שבעה אלא לביאה ראשונה. 7) — But perhaps go in this direction: she becomes tamei and she confers tumah upon her cohabiter. Just as she counts the seven days only from the first sighting (even if she had other sightings all seven days), so, when he becomes tamei by a niddah, he should count seven only from the first union.
נראה למי דומה – דנים טומאה שהיא ממקום אחר מטומאה שהיא ממקום אחר, ואל יוכיחו דמים שהם מגופה. 8) Let us see whom he most resembles, viz.: We derive tumah which is from a different source (the niddah) from tumah which is from a different source (a dead body), and this is not to be refuted by blood, which is from her own body.
או כלך לדרך זה: דנים טומאה שהיא מחמת דמים מטומאה שהיא מחמת דמים ואל תוכיח טומאת המת שאין מחמת דמים ת"ל "וטמא שבעת ימים" – שיספור שבעה לביאה אחרונה. 9) Or go in this direction: We derive tumah which is caused by blood, from tumah which is caused by blood, and this is not to be refuted by dead body tumah, which is not caused by blood. It is, therefore, written "and (after the "lying") he shall be tamei for seven days." He counts seven days from the last union.
[י] "וכל המשכב אשר ישכב עליו יטמא" – יכול יטמא משכב שאינו מיוחד לשכיבה ומושב שאינו מיוחד לישיבה? לא! מה היא אינה מטמאה אלא משכב המיוחד לשכיבה ומושב המיוחד לישיבה, אף הוא לא יטמא אלא משכב המיוחד לשכיבה ומושב המיוחד לישיבה. 10) "and every mishkav on which he lies shall be unclean." (and everything that he sits upon shall be unclean). I might think that he confers tumah upon a mishkav that is not distinctive for reclining and a moshav that is not distinctive for sitting. No — Just as she confers tumah only upon a mishkav that is distinctive for reclining and upon a moshav that is distinctive for sitting, so, he.
[יא] יכול היא והוא לא יטמאו טומאה חמורה אבל היא והוא יטמאו טומאה קלה? ת"ל "המשכב". אין לי אלא משכב, מרכב מנין? ת"ל "וכל". אין לי אלא בזמן שהוא שוכב עליו ונוגע בו. מנין למשכבות עשרה זו על גב זו? על גב אבן מסמא? ת"ל "וכל". "המשכב אשר ישכב עליו" – עד שינשא רובו עליו. 11) I might think that both she and he do not confer stringent tumah but both confer only lesser tumah (See 3 above); it is, therefore, written (Vayikra 15:24) "mishkav … yishkav," (which connotes both types). This tells me only (of his conferring tumah) when he is lying upon it (the moshav) and touching it. Whence is the same derived (for a situation) where there are ten layers (of moshav) one atop the other, even with a stone intervening? From "on every mishkav on which he lies."