Hebrews 6:17-19 HCSB
Because God wanted to show His unchangeable purpose even more clearly to the heirs of the promise, He guaranteed it with an oath, so that through two unchangeable things, in which it is impossible for God to lie, we who have fled for refuge might have strong encouragement to seize the hope set before us. We have this hope as an anchor for our lives, safe and secure. It enters the inner sanctuary behind the curtain.
HCSB: Holman Christian Standard Bible