Hi Toby!  Yes, I think there is a biblical reference to this somewhere--I havent found it yet, but the version I know is about swearing, or taking an oath--swearing not in the sense of foul language, by the way.  I'll try to find it.

In the meantime, here's something:

""To make a vow for life is to make oneself a slave".  Voltaire, in his Philosophical Dictionary of 1764.  (He knew that, and that long ago!!!!)

Also, "Promises and pie-crust are made to be broken".  Jonathan Swift.

Cheers,

Shelagh