2 Bible Verses about Covenant Obligations

Again, you have heard that it was said to the ancients: You shall not swear falsely, but shall pay to the Lord your vows. But I say to 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:read more.
neither shall you swear by your head, for you can not make one hair white or black. But let your word be, Yes, yes; No, no; for whatever is more than these is of the Evil One.

Brethren, I speak of things common among men: No one sets a covenant aside, or enjoins any thing additional after it is confirmed, though it be a man's covenant.