Translations
Wherein God, willing more abundantly to shew unto the heirs of promise the immutability of his counsel, confirmed it by an oath:
Likewise, Elohim, desiring to show even more fully to the heirs of the promise the unchangeable nature of His purpose, guaranteed it with an oath,
Because God wanted to make it absolutely clear to the heirs of His promise that His purpose would never change, He backed it up with a sworn oath —
So 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.

