God said it. He is the best one to know, since He is the center of righteousness and all other attributes of God.
Please explain how you know that "God said it." Don't you really mean to say, "you believe God said it"; please be precise within your communications skills without offering mere conjecture, speculation and other unsubstantiated ideas.
I know it because I know there is a God who is sovereign over His Universe. Anyone who has a relationship with God knows He exists. A child of Satan cannot believe because Satan has a blindfold over his eyes. I suppose you cannot understand this type of evidence, and I should be patient with you. Not only are you blind to God, but you are condemned and your eyes will be opened when you stand before God at His Judgement Seat. The best that any Christian can do for you is pray for you.