What does Hebrews 11:5 mean?

The writer of Hebrews is explaining how faith leads to God's blessings. The first set of examples used are meant to show that God rewards those who seek Him, despite not having a crystal-clear understanding of how or when His promises will be fulfilled. The first example given was that of Abel, who offered God an acceptable and faithful sacrifice (Genesis 4:3–5). Even though Abel was killed by his jealous brother, Cain (Genesis 4:8–10), God honored Abel's faith, and his story has become a useful lesson for us all.

Here, the writer offers a drastic contrast in Enoch. So far as we can tell from his appearance in the book of Genesis, Enoch did not experience physical death—instead, he was "taken" by God (Genesis 5:23–24). While Abel suffered the worst possible end to his earthly experience, being violently murdered, Enoch never had to die at all. The example given by Enoch is that he so "walked with God" that he was taken before death. Crucially, the writer of Hebrews points out that it was Enoch's faith which motivated his behavior.

The contrast between Abel and Enoch is important. Both are recipients of God's acceptance, though their earthly lives came to radically different ends. The theme of this part of Hebrews is that faith "looks forward" despite incomplete knowledge. Though we cannot see all ends, here and now, God is moving towards an eventual fulfillment of all promises. What happens during our earthly lives is only a part of that process, not the end of it. As a result, believers are not guaranteed success in the mortal world.