What does Hebrews 6:18 mean?
The first part of this verse refers to "two unchangeable things" which prove that God's oaths are absolutely reliable. One of these is the very nature of God: He is all-powerful (Psalm 68:34; Job 42:2), He cannot change (Malachi 3:6), and He cannot lie (Numbers 23:19), therefore whatever He promises is absolutely certain. The second item is the evidence of His truth as given in His word; this means real-world history as described by the Bible. That which God has promised to do, history proves He actually has done. In the case of the original readers of Hebrews, this includes seeing how God fulfilled His promises, even if Abraham did not live to see all of them completed.The second part of this verse begins an interesting combination of images, used to describe the level of confidence Christians can have in the promises of God. The first image, given here, is that of fleeing to a refuge. In the Old Testament, there were cities of refuge where fugitives could run in order to escape vigilante justice (Numbers 35; Joshua 20). People of that era also used fortified buildings, caves, or cliffs as safe-houses against invaders or disasters. As it applies to the Christian experience, this suggests the idea of escaping death, or at least the condemnation brought by the world.
Later verses will add two additional images to this statement. First is that of an anchor, which represents hope and security. The other is the inner sanctuary of the Temple, something the book of Hebrews will mention frequently (Hebrews 6:19; 9:11–12).