I believe you were in Leviticus with this when they were given rules and guidelines on means of healthy living.... First of all I want to say that the rules and guidelines were necessary because they had not the means for sterilizing and disinfecting and cleaning as, for example, we do. Heck.. mold is even covered in this book. This said, I think this analogy is used incorrectly. The question in this forum is whether or not masterbatin is sinful. To say that the bible doesn't mention that one is unclean after masterbation is the same as the bible not saying it is sinful would imply that the bible is saying that menstruation is sinful. Menstruation is not sinful... just unclean. I am not bible expert, but if you look up original text I am willing to bet that the word used for unclean in your reference is different from unclean when referred to someone's spiritual state. For example... to have dirt on you is not sinful but to be a "dirty ole man" is.
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ah yes... I remembered I got a bible dictionary/concordance the other day and looked up unclean. Here is what it says... in brief:
Unclean as an adjective - tame' This adjective occurs usually in Leviticus, with the meaning of ceremonial or ritual cleanness. In otherwords referring to your hygeine. and it even mentiones Lev. 15:2, 25 here in reference to gential issues - this whole chapter deals with bodily discharge including semen and menstruation.
Unclean as an adjective - akathartos This refers to being uncleal morally.