2 Bible Verses about Covenant Obligations

"Again, you have heard that it was said to the ancients, 'Thou shalt not swear falsely, but shalt perform thy vows to the Lord.' But I tell you not to swear at all; neither by Heaven, for it is God's throne; nor by the earth, for it is the footstool under His feet; nor by Jerusalem, for it is the City of the Great King.read more.
And do not swear by your head, for you cannot make one hair white or black. But let your language be, 'Yes, yes,' or 'No, no.' Anything in excess of this comes from the Evil one.

Brethren, even a covenant made by a man--to borrow an illustration from daily life--when once formally sanctioned is not liable to be set aside or added to.