So when God desired to show more convincingly to the heirs of the promise the unchangeable character of his purpose, he guaranteed it with an oath, so that by two unchangeable things, in which it is impossible for God to lie, we who have fled for refuge might have strong encouragement to hold fast to the hope set before us. (Hebrews 6:17–18)
Why does the writer of Hebrews encourage us to hold fast to our hope? If the final enjoyment of our hope was obtained and irrevocably secured by the blood of Jesus, then why does God tell us to hold fast?
The answer is this:
What Christ bought for us when he died was not the freedom from having to hold fast, but the enabling power to hold fast.
What he bought was not the nullification of our wills as though we didn’t have to hold fast, but the empowering transformation of our wills so that we want to hold fast.
What he bought was not the canceling of the commandment to hold fast, but the fulfillment of the commandment to hold fast.
What he bought was not the end of exhortation, but the triumph of exhortation.
He died so that you would do exactly what Paul did in Philippians 3:12, “I press on to make it my own, because Christ Jesus has made me his own.” It is not foolishness, it is the gospel, to tell a sinner to do what Christ alone can enable him to do; namely, hope in God.
So, I exhort you with all my heart: Reach out and take hold of that for which you have been taken hold of by Christ. Hold it fast with all your might — which is his might. His blood-bought gift of your obedience.