When God made his promise to Abraham, since he had no one greater to swear by, he swore by himself,
the oath he swore to Abraham our father, to grant us
Brothers, let me give an example from everyday life: When a man-made covenant is ratified, no one annuls it or adds to it.
For if the inheritance comes by the law, it no longer comes by the promise; but God granted it to Abraham by a promise.