Living Under Oath - Audio

In the Sermon on the Mount, Jesus had a formula it seemed. "You've heard it been said...I say..." And in each commandment, Jesus went from outward action (fruit), to inward desire (tree). So not only is committing adultery wrong, but thinking about it is. The same with murder. What about oaths? What is Jesus, and James after him, getting to when it comes to oath-taking? Is it a strict forbiddance of the action, or is there a heart problem being addressed here?