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.
I know it because I know there is a God who is sovereign over His Universe.
Don - you have used redundancy and restatement as a method to provide support for your argument; if you allow me to parse your statement, I shall explain "why" ---
I know it
This partial sentence sets the foundation for your approach that you intend to establish ---
because
Sets the framework for supporting data within the context of your earlier foundation; this substructure of the sentence is the declarative or refinement of the conjugative context ---
I know there is a God
Is a restatement of the earlier foundation by mere substitution of "it" with "there is a God"; this is redundant and nothing more than restatement with substitution. You have ineffectively added to anyone's understanding about supporting mechanisms for your presentation. But you don't stop at your own nonsupportive discussion, you struggle by attempting to clarify your brief definition of "God" ---
who is sovereign over His Universe.
This is an unfortunate structural attempt at limiting "God" in the context of "His Universe" because your struggle for clarification actually confuses any reader of your post, i.e. infers other universes; furthermore your point infers that your belief of a "Satan" as the master of his or its own Universe may bridge all of humanity with God's eternal war against Satan with humanity caught in the middle of of "good" vs. "evil" battle which is a dualistic principle that I earlier introduced to you.
The obvious error with your attempt to explain or clarify God's role about the Universe is that you position God as far from being sovereign of or about humanity or the Universe since there is an interactive characteristic that reflects some sort of meaningful conflict between "His Universe" and some other Universe or even many other Universes; this means the conflict may have infinite relationships; which means God does not possess any more sovereignty about the world around us than anyone else, including yourself. In other words, if such conflict is true, you imply God is limited and therefore God does not possess the power that you profess.
I find your first statement to be redundant and revealing of a contradictory nature. For the rest of your post, I shall ignore altogether as you don't have the knowledge that you profess to have; you may believe your knowledge but you can't explain your way out of a wet paper bag to use a borrowed and often overused cliché.