Hebrews 6:17

‘Wherein God, being minded to show more abundantly to the heirs of the promise the immutability of his counsel, interposed with an oath,’

And that is why, when God determined to show in the most certain manner to those who were the heirs of promise the unchangeableness of what He had determined to do, He did it by means of an oath in order to demonstrate that there was no way in which He would alter what He had determined.

The impression given here is that those heirs of promise were already fixed and determined in the mind of God, and that His oath was being made to them as well as to Abraham. He was speaking to them as much as to Abraham. Those who are His now can look back and see themselves as there in Abraham, receiving the promise. And that is why they can have full assurance of God’s faithfulness to them.

‘The immutability of His counsel.’ He wanted all to know that what He had determined to do He would do, that what He promised He would perform, because it was His unchangeable will. Thus do we recognise that it was not left to chance, or to the will of man, but was determined by God in every detail.