Verily, verily, I say unto you, if you desire a further witness, cast your mind upon the night that you cried unto me in your heart, that you might know concerning the truth of these things.
Did I not speak peace to your mind concerning the matter? What greater witness can you have than from God?
Doctrine & Covenants 6:22-23
Read in scriptures: http://bit.ly/1jkCXxr