“There is a statement often repeated in the Church, and while it is not in one of the Standard Church Works, it is accepted as church doctrine, and this is: ‘As man is, God once was; as God is, man may become.’”
LeGrand Richards, Letter to Morris L. Reynolds – 14 July 1966; cited by Tanner in Mormonism: Shadow or Reality (Salt Lake City, UT: UTLM, 2013), 164.