He taught them as one having authority. (Mark 1:22)
From of old, the Almighty promised that a voice would ring out which would carry the divine guarantee of truth. He made this promise to a people like us: a people seeking the Promised Land, needing to hearken to the divine voice in order to find our way.
What if no voice of truth guided us? What if the only source for truth was me myself?
That would be a sketchy situation. I would want to have one set of rules when I was in one mood, and a different set when I was in another. Hungry? One set of rules. Angry? A different set. Eyes fixed on a toy I want to play with? Another set. Life without the voice of God would leave a person fat, friendless, and maxed-out with credit-card debt.
Thank God, then, that He speaks to us. With authority. He speaks to us with the authority of the final judge, before Whom we will have to answer for everything done or left undone.