A Jewish man called his mother in Florida, “Mom, how are you?” “Not too good,” said the mother, “I’ve been very weak.” The son asked, “Mom, why are you so weak?” She replied, “Because I haven’t eaten in 27 days.” The son said, “That’s terrible. Why haven’t you eaten in 27 days?” The mother answered, “Because I didn’t want my mouth to be filled with food if you should call!”
Source: http://www.enlightened-spirituality.org/Spiritual_Humor.html