In Psalm 3:3 David said: “But You, YHWH, are a shield about me …”. It is instructive that the enemies of David, the “naysayers”, said: “There is no help for him in God” — the word “God” there is the Hebrew “Elohim”, which is a general name for God. But in his response, David said, “But you, O YHWH, are a shield for me …”. YHWH, of course, is the personal, covenant name of God, the name He gave Moses when he asked Him what His name was.
So the substantial difference between David and his enemies was that they something about “a god” – but David KNEW God personally. This is always the crucial difference in religion. Many people know something of a “God” and speculate on what they think He will or will not do — but they have no basis for their speculations. They don’t know HIM as He has revealed Himself personally. David knew Him this way, and so can we: through the Bible, and through Jesus Christ. Knowing Him, we can say like David to the speculations of our enemies: “But YOU O YHWH are a shield about me; my Glory, and the Lifter of my head”!