Today's teaching is about making vows, promises, swearing, taking an oath, however you want to call it.  Jesus' teaching is relevant today about letting your yes be yes, and your no be no.  If your committed, then your word should be good enough.  Does our practice and behavior lend credibility?  Of course it does, so we build our "word" based on what "we do."  Of course, there is such a thing as "over committing" as well.