The Billy Graham Rule is a guideline the Reverend Billy Graham followed in his own life that became known by his followers and popularized as a way to maintain a healthy and secure marriage. Graham's rule is to never be alone with a member of the opposite sex to which a person is not married.
More About The Billy Graham Rule
The Billy Graham rule is presented as a way to prevent infidelity by avoiding even the "appearance of evil." In some communities, the rule is held up as the ideal while in others it is increasingly viewed as impractical and unnecessarily restrictive.