“Hebrews is all about persevering in sanctification. Without holiness, writes the author, ‘no one will see the Lord.’ We must therefore ‘strive’ for it (Hebrews 12:14).
He uses vigorous language. His verb (διώκω, strive) appears regularly in the New Testament with the sense of ‘persecute.’
Such strong language was needed here because these Christians were facing hardship and opposition. They therefore needed to pay careful attention to the gospel, to digest what they had heard, so that they would not drift away.
What do you need to do to slow down and go backwards in the Christian life? Hebrews’ answer is: ‘Nothing.” Drifting is the easiest thing in the world.
It is swimming against the tide that requires effort. And the Christian life is against the tide all the way. Spiritual weariness, being ‘sluggish,’ is one of our great enemies. The author is all-too-familiar with its tell-tale signs.
Christians then, as now, were confronted by many pressures. Some of them had suffered deeply for their testimony to Jesus Christ. We might think that anyone who has withstood trials would be in no danger of failing to persevere.
But the battle to be holy is fierce, the opposition is strong, and the obstacles are many. Even those who have won great victories in the past can become weary. Spiritual lethargy can set in, and we begin to drift.
We constantly need to be encouraged to keep going (Hebrews 3:12-13).”
–Sinclair Ferguson, Devoted To God: Blueprints For Sanctification (Carlisle, PA: Banner of Truth Trust, 2016), 191.