2 Bible Verses about Covenant Obligations

Again, ye have heard, that it was said to the ancients, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths: but I say unto you, swear not at all; neither by heaven, for it is the throne of God; nor by the earth, for it is his footstool; nor by Jerusalem, for it is the city of the great King: neither shalt thou swear by thy head,read more.
for thou canst not make one hair of it white or black: but let your conversation be yea, yea; no, no; for whatever is more than these, cometh from the evil one.

Brethren, (I speak after the manner of men,) no one cancelleth or addeth to a covenant which hath been ratified, though it be but the covenant of a man.