Jesus didn't say, "Whosoever shall speak to God about this mountain." He said we should speak directly to the mountain the desired end result.
From a worldly point of view, that sounds foolish. But 1 Corinthians 1:27 explains that God has chosen the foolish things of the world to confound the wise. It's always going to sound foolish to the world when a Christian talks as if what God has promised is reality, especially when those promises seem to contradict the natural evidence around us. But if you want to keep the enemy defeated, that's the kind of talking you'd better be doing.
