The Karezza Method, by J. William Lloyd [1931], at sacred-texts.com
Always in the sexual life there should be cleanness - that innocence, kindness, justice of feeling which instinctively prefers any sacrifice of immediate passional pleasure rather than befoul or degrade a high ideal, or to jeopardize the physical or spiritual health of the beloved, or of self, or of the tenderly considered, possible unborn.
Cleanness expresses itself in a reverent regard and considerate self-control at all times, concerning all things, thoughts, motions and relations of sex, and the conscientious use of all organs and functions in the service of the soul's ideal.
The clean may be mistaken, but whatever they do they cannot be impure.