Taking an Oath

This question comes from Grand Rapids. Scripture says thou shalt not swear in Matthew 5:33-37. How does that relate to our taking an oath? To begin we should quote the text: “Again, ye have heard that it hath been said by them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths: But I say unto you, Swear not at all; neither by heaven; for it is Gods throne: Nor by earth; for it is his footstool; neither by Jerusalem; for it is the city of the great King....