2 Bible Verses about Covenant Obligations

Again, you have heard that it was said by the ancients, You shall not swear falsely, but shall perform to the Lord your oaths. But I tell you, Swear not at all; neither by heaven, for it is God's throne; nor by the earth, for it is his footstool, nor by Jerusalem, for it is the city of the great King;read more.
nor swear by your head, for you cannot make one hair white or black. But let your speech be, yes, yes, and no, no; for any thing more than this is evil.

Brothers, I speak according to man. But no one abolishes a man's covenant when it is established, or makes additions to it.