If there ever was a thing revealed to man perfectly, clearly, so that there could be
no doubt or dubiety, this was revealed to me, and it came in these words: “As man now is, God once was; as God now is, man may be.” This may appear to some minds as something very strange and remarkable, but it is in perfect harmony with the teachings of Jesus Christ and with His promises. — President Lorenzo Snow, General Conference, October 1898
It is the first principle of the Gospel to know for a certainty the character of God, and to know that we may converse with him as one man converses with another, and that he was once a man like us; yea, that God himself, the Father of us all, dwelt on an earth, the same as Jesus Christ himself did. . . .
I will go back to the beginning before the world was, to show what kind of a being God is. What sort of a being was God in the beginning? Open your ears and hear, all ye ends of the earth . . .
God himself was once as we are now, and is an exalted man, and sits enthroned in yonder heavens. That is the great secret. If the veil were rent today, and the great God who holds this world in its orbit, and who upholds all worlds and all things by his power, was to make himself visible, – I say, if you were to see him today, you would see him like a man in form – like yourselves in all the person, image, and very form as a man. — Teachings of the Prophet Joseph Smith, pp. 345-346