Website PLATE-FULL CHAIRS
[23b middle] Braisa: One who is Tamei (spiritually impure) [that can transfer impurity via sitting on objects], can only transmit impurity onto items that are normally sat upon [ie: a chair or a pillow, but not a plate].
http://aurorabachelet.it/Educareistruendo/tabid/59/Default.aspx E’s Lesson: Items that are used for purposes other than they were designated for not only do not complete the proper job, but also get broken in the process [like sitting on a plate]. When people lust after immoral and improper objects and activities, their bodies never fully accomplish what they want to achieve (their desires are never fulfilled completely) and they get harmed in the process. Hashem gives us wonderful tools (our bodies) to perform amazing spiritual tasks (the Mitzvos) and we should always take care and use them properly.