Charles Spurgeon Commentary Hebrews 12:14-15

"Follow after peace with all men, and the sanctification without which no man shall see the Lord: looking carefully lest [there be] any man that falleth short of the grace of God; lest any root of bitterness springing up trouble [you], and thereby the many be defiled;" — Hebrews 12:14-15 (ASV)

And holiness, without which no man shall see the Lord: looking diligently lest any man fail of the grace of God;

"Lest he should come short of the grace of God," and as it were fall back. Paul is still keeping to his illustration drawn from the wrestling at the Olympic games. Sometimes, the wrestler gave his opponent a back fall, and down he went, and so lost the crown; beware that such a fall does not happen to you in your spiritual wrestling.