Friendship must be physically dirty if it is to be morally clean.
 G. K. Chesterton, What's Wrong with the World (1910). copy citation

Context

“it must lead to these things so long as it is honorable; comradeship must be in some degree ugly. The moment beauty is mentioned in male friendship, the nostrils are stopped with the smell of abominable things. Friendship must be physically dirty if it is to be morally clean. It must be in its shirt sleeves. The chaos of habits that always goes with males when left entirely to themselves has only one honorable cure; and that is the strict discipline of a monastery. Anyone who has seen our unhappy young idealists in East End Settlements losing their collars in the wash and living on tinned salmon will fully understand why it was decided by the wisdom of St.” source