What does Hebrews 6:15 mean?

As weak, limited people, we have a tendency to expect immediate results. Even if we know, intellectually, that some things take time, we still drift into doubt when events don't play out according to our preferred schedule. The worst outcome of this human flaw is despair: to assume that, since a promise has not yet been fulfilled, that maybe it never will be. Or, that there was no truth behind the promise in the first place.

The book of Hebrews was written to persecuted Jewish Christians. They faced pressure to abandon the promises of their Christian faith. For some, this was especially dangerous; doubt and spiritual immaturity placed them at risk of "falling away." A major component of solving this problem, according to the writer, is a purposeful approach to growing in both truth and love. This requires confidence: a personal conviction that what we're seeking after is true.

For these same Jewish believers, there would have been no greater example of patient faith than Abraham. He waited a long time to see God's promises fulfilled (Genesis 12:7; 17:5; 18:18; 22:16–18). In some cases, God did not completely fulfill those oaths until after Abraham had died. The Greek term used here for "patience" is makrothymēsas, which includes the idea of tolerating abuse from others without retaliating. In other words, Abraham needed to be patient towards his situation, and his struggles, while waiting for God to make good on His word. This purposeful, trusting, confident faith is presented as a mirror-image to the laziness denounced in Hebrews 5:11 and Hebrews 6:12.

Fortunately, history would show that God's vows are unbreakable. This was meant to give the original readers of this letter confidence. Even more than Abraham, they had evidence that God's Word, and His oaths, are absolutely proven true. Despite persecution, and what felt like a delay in God's rescue, they could trust in Him. The ultimate "anchor" for this hope, explained in the next passage, is found in Jesus Christ.