Commento su Levitico 15:23

ואם על המשכב הוא AND IF ONE BE ON HER PLACE OF REPOSE [OR ON ANY THING WHEREON SHE SITTETH] — This means, one who sleeps or sits on the place where she has slept or has sat even though he does not directly touch it (e. g. if there are covers upon the couch or the seat; for if he touches it vv. 21 and 22 apply); he also comes under the law of uncleanness that is stated in the above verse — that he requires washing of garments.

'ואם על המשכב הוא וגו, if some sits or lies on something even indirectly in contact, מדרס, with the afflicted person chair or bed, etc., he will still become ritually contaminated by such indirect contact בנגעו בו יטמא עד הערב, even if the “contact” was so indirect as instead of sitting on the contaminated item one sat on a saddle supported by the contaminated item, the ritual impurity lasts until evening when immersion in a ritual bath removes it. He is then, however, not of a sufficiently severe degree of ritual impurity to contaminate clothing (even his own) over and beyond his body. In other words, in this kind of scenario the Torah did not add that he has to wash (immerse) his garments in order to become ritually pure again. (as it had done in verse 21 and 22, for instance)

Even if he did not touch [it]. This is as Rashi explains above (v. 6) regarding: “Whoever sits on the vessel” — “even if he did not touch [it].” Above (ibid.), I explained Rashi’s proofs that lying down and sitting cause impurity even though he does not touch the vessel. Rashi’s view is thus: Do not think that [the phrase] “when he touches it he shall be impure until the evening,” which it says after [the phrase], “If he is on the bed...” implies that even if he touches the bed, chair, or saddle he does not require washing clothes, and the explanation of the word “it” would be: “in each one of them.” This cannot be, for it does not refer to “If he is on the bed...” This is because even if he does not touch it he requires washing clothes. We need not ask: To what does the phrase “when he touches it he shall be impure until the evening” refer? Therefore Rashi explains: “On the vessel — to include...” I.e., why does it need to say, “on the vessel”? It only needs to say, “that she is sitting on.” Rather [it must be]: “To include a saddle.” If so, that which is written, “when he touches it...” refers to a saddle, as Rashi explains later that it does not require washing clothes.

ואם על המשכב הוא, “if he is on the bed (of his partner) with most of his body.” (Sifra) Some commentators understand the word הוא in this verse as referring to the person who has contracted the disease of involuntary seminal emission. According to them, we must understand the verse as follows: “if that blood which was on the couch or on any chair on which the woman in question has sat after having experienced the symptoms has now been touched or even if he touched the vessel or chair on which she had sat, he will remain ritually impure until nightfall after he has immersed himself in a ritual bath. Let us quote a practical example, using verse 17. We read there: וכל בגד אשר יהיה עליו שכבת זרע, “and every garment on which has come moist human semen, (Jewish) etc.,” you might well ask why this verse has been written at all. If someone who has only come into contact with the garment that had been stained with semen by its wearer has thereby become ritually impure, how much more so will someone who has been lying with the body from which this blood was emitted does not have to undergo purification rites? Answer: Jewish law does not permit a judge to impose a penalty based only on logic; unless the penalty has been spelled out in the Torah it cannot be imposed (as the guilty party will plead ignorance of the law.) We find the same thing Numbers 19,14: וכל הבא אל האהל וכל אשר באהל יטמא, “anyone entering such tent (containing a corpse) will become ritually defiled.” The beginning of the verse refers to someone whose body has partially entered the covered airspace within which the corpse lies. The second part speaks of someone whose entire body is within that airspace. It is no more than logical that the second party will not have to do less than the first party in order to purify himself. Nonetheless, because of the rule we just mentioned, the Torah had to spell this out.

על הכלי UPON A VESSEL — This is intended to add to משכב and מושב any article for riding on (Sifra, Metzora Parashat Zavim, Section 4 15).

ואשר היא יושבת עליו, our sages (in Torat Kohanim zavim 4,18 understand this as referring to the relatively low level of ritual contamination called טומאת מרכב, see beginning of this verse).

בנגעו בו WHEN HE TOUCHETH IT — "it" (בו) — this refers only to מרכב which, as has just been stated, is included in the law on account of the words על הכלי.

בנגעו בו יטמא WHEN HE TOUCHETH IT HE SHALL BE UNCLEAN, but does not require washing of the garments, because so far as the מרכב is concerned its being touched does not communicate uncleanness to people so that they in turn should render their garments unclean (cf. Mishnah Kelim 23:3).