Leviticus 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. 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). 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).

וְאִ֨ם עַֽל־הַמִּשְׁכָּ֜ב ה֗וּא א֧וֹ עַֽל־הַכְּלִ֛י אֲשֶׁר־הִ֥וא יֹשֶֽׁבֶת־עָלָ֖יו בְּנׇגְעוֹ־ב֑וֹ יִטְמָ֖א עַד־הָעָֽרֶב׃

And if it be on her bed, or on anything whereon she sits, when he touches it, he shall be unclean until evening.