G0276–ἀμετάθετος–ametathetos

So that when it was God's desire to make it specially clear to those who by his word were to have the heritage, that his purpose was fixed, he made it more certain with an oath;

ἀμετάθετον ametatheton “unchangeableness”

So that we, who have gone in flight from danger to the hope which has been put before us, may have a strong comfort in two unchanging things, in which it is not possible for God to be false;

ἀμεταθέτων, ametathetōn “unchangeable,”