Sorry about this being down a week. I think they finally got things straightened out.
Jesus told His followers that the religious officials were usurping the position of Moses. He further commanded them to obey that which these fellows taught (presumably as long as it did not counter Scripture) but NOT to do as they did. Their focus was on glory to self and not to God. To emphasize this fact, as He prounounces woes upon them, he calls them hypocrites. They in fact are sons of hell (v. 15).
Swearing is not what we want to say that it is, but it is what the words actually mean (v. 16). In all swearing (calling down an oath upon ourselves to verify the veracity of what we speak) we are calling God as witness. We must not be hypocritical in any way.