13When God made His promise to Abraham, since He had no one greater to swear by, He swore by Himself,
14saying, “I will surely bless you and multiply your descendants.”
15And so Abraham, after waiting patiently, obtained the promise.
16Men swear by someone greater than themselves, and their oath serves as a confirmation to end all argument.
17So when God wanted to make the unchanging nature of His purpose very clear to the heirs of the promise, He guaranteed it with an oath.
— Hebrews 6:13-17