2 Bible Verses about Covenant Obligations

"Again you have heard that it was said to those of old, 'You shall not swear falsely, but shall perform your oaths to the Lord.' But I say to you, do not swear at all: either by heaven, for it is God's throne; or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King.read more.
And do not swear by your head, for you cannot make even one hair white or black. Simply let your 'Yes' be 'Yes,' and your 'No,' 'No'; anything more than this comes from evil.

To give a human example, brethren: even though it is only a man's covenant, yet when it has been ratified, no one sets it aside or adds conditions to it.