It does not come from the bible. In fact, until the time of the renaisance, bathing was oft seen as sinful, regarding the body as more important than the spirit. Bathing was also strongly associated with the "decadent" Romans. It's origins seems to be in the writings of Francis Bacon. In his 'Advancement of Learning' (1605) he wrote: 'Cleanness of body was ever deemed to proceed from a due reverence to God.' Near two centuries later John Wesley in one of his sermons (1791) indicated that the proverb was already well known in the form we use today. Wrote Wesley: 'Slovenliness is no part of religion.'Cleanliness is indeed next to Godliness.'" From "Morris Dictionary of Word and Phrase Origins" by William and Mary Morris (HarperCollins, New York, 1977, 1988). There are a couple more details in "Random House Dictionary of Popular Proverbs and Sayings" (1996) by Gregory Y. Titelman (Random House, New York, 1996): ".According to the fourteenth edition of 'Brewer's Dictionary of Phrase and Fable,' it is an old Hebrew proverb used in the late 2nd century by Rabbi Phinehas ben-Yair. First attested in the United States in the 'Monthly Anthology and Boston Review' (1806). The proverb is found in varying forms."