2 Bible Verses about Covenant Obligations

Again you have heard that it was said to the ancients, Thou shalt not swear falsely, but shall perform unto the Lord thine oaths. But I say unto you, Swear not at all; neither by heaven, because it is the throne of God; nor by the earth, because it is the footstool of His feet; neither by Jerusalem, because it is the city of the great King.read more.
Neither swear by thy head, because thou art unable to make one hair white or black. But let your speech be, Yea, yea; Nay, nay; but that which aboundeth more than these is of the evil one.

Brethren, I speak according to a man, nevertheless no one disannuls, or adds to, the covenant of a man which has been confirmed.