Is cleanliness next to Godliness?

I've been ardently searching the Bible for a proverb my wife keeps quoting. But somehow, I don't think it is in there. So, where did the notion that being clean had anything to do with being holy? I like to tell my wife that only my feet need to be clean (I know where that is in the Bible). Looking for historical answers from a Catholic tradition or if it really is in the Bible that would be good too. What I'd really like to know is how clean is clean enough not to be a slothful slob and how clean is so clean that you miss out on the "better part" that Jesus said Martha was missing out on.