2 Bible Verses about Covenant Obligations

"Again ye heard that it was said to the ancients, You shall not swear falsely, but shall perform to the Lord your oaths;" but I say to you, Swear not at all; neither by Heaven, because it is God's throne; nor by the earth, because it is His footstool; nor by Jerusalem, because it is the Great King's city;read more.
neither swear by your head, because you can not make one hair white or black. But let your speech be, 'Yes, yes;' 'No, no;' and what is more than these is of the evil one.

Brethren, I am speaking after the manner of man: even a man's confirmed covenant no one sets aside, or adds thereto.