Midrash sa Levitico 15:21: Sifra

וְכָל־הַנֹּגֵ֖עַ בְּמִשְׁכָּבָ֑הּ יְכַבֵּ֧ס בְּגָדָ֛יו וְרָחַ֥ץ בַּמַּ֖יִם וְטָמֵ֥א עַד־הָעָֽרֶב׃

At sinumang humipo sa kanyang higaan ay maglalaba ng kanyang mga kasuotan at maliligo sa tubig, at magiging marumi hanggang sa gabi.

Sifra

11) (Vayikra 15:20) "And all that she lies upon in her niddah state shall be unclean, and all that she sits upon shall be unclean": I might think that she confers tumah upon a mishkav that is not distinctive for reclining upon and upon a moshav (a seat) that is not distinctive for sitting upon. It is, therefore, written (Vayikra 15:21) "And whoever touches her (distinctive) mishkav shall wash his clothes."
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Sifra

12) (Vayikra 15:22) "And whoever touches any object that she sits upon shall wash his clothes": Just as below (i.e., Vayikra 15 verse 21, which elucidates verse 20), she confers tumah only upon a mishkav that is distinctive for lying upon and a moshav that is distinctive for sitting upon, here, too, she confers tumah only upon a mishkav that is distinctive for lying upon and a moshav that is distinctive for sitting upon.
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