Hebrews 6:16-18

161For people swear an oath by 2one greater than themselves, and with them 3an oath serving as confirmation is an end of every dispute.

174In the same way God, desiring even more to demonstrate to 5the heirs of the promise 67the fact that His purpose is unchangeable, 8confirmed it with an oath,

18so that by two unchangeable things in which 9it is impossible for God to lie, we who have taken refuge would have strong encouragement to hold firmly to 10the hope set before us.