This makes sense from a
psychological perspective too, as most of
Jesus' stuff does.
Swearing vows is an
overcompensation--it allows us to metaphorically
place a
thing between
us and our words, thereby
removing us by one step from our
promises. It's almost like
handing off the responsibility, as if when you say, "I swear by
all that's holy", you're somehow
foisting the
responsibility of the
truth of your statement off onto the
holy things.
Jesus tells us it's plain
disrespectful for
us to swear by
God or
God's emanations. This makes sense two ways: It may
devalue God or God's
creations to use them in this way. It also
definitely devalues one of God's creations in
particular--Us. When we
use other things to
buffer our statements and
give them
artificial power, we are
admitting our lack of faith in our
own words. According to
Christ, if we had but the
faith of a mustard seed, we could do
everything he does. Not having enough faith to
believe your own words isn't the way to get there, apparently.
Jesus knew, I bet, that it takes
great courage to simply say "yes" or "no" and leave it at that. It
requires that we
honor ourselves enough to understand that
our word is
holy in its own way,
because we are (remember?)
in the image of
God. But of course, if we had even
that much faith to begin with, apparently we could
move mountains!