V. 15.— Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble you, and thereby many be defiled. Looking...— We ought to maintain a holy jealousy over ourselves, knowing how prone we are to sin and to apostasy, and that our adversary, the devil, goeth about like a roaring lion, seeking whom he may devour; but the Apostle appears to have in view our watching over each other in love. The precept is in direct opposition to the question, “ Am I my brother’ s keeper?” The word is repeatedly rendered “ come short,” Romans 3:13; Hebrews 4:1. It is in the margin “ fall from;” and, indeed, while we may be confident that He who hath begun a good work will carry it on to the day of Christ, and that the election shall obtain eternal life, we can only know that we are the subjects of Divine grace by holding fast the truth as it is in Jesus, and abiding in the doctrine of Christ. “ For some receive the word with joy, but have no root, and in time of temptation fall away;” and although there is an essential difference between saving and temporary faith, it may be impossible for a time to distinguish them. Empty professors go out from believers, because they were not of them; had they been so, they would no doubt have continued with them; but, in the meantime, their profession and practice may be such as to make it meet for others to think that God has begun a good work in them. But, from the connexion of the passage, it would appear that the Apostle is treating of that watchfulness which believers are commanded to exercise over their brethren; not watching for each other’ s halting, but, knowing the temptations and dangers to which all are exposed, not only to mind their own things, but the things of others, and to be prepared to caution those who are exposed to peculiar temptations; at least, this is included in the precept; and they were not only to obey this exhortation from regard to their brethren, for they were personally concerned. One sinner destroys much good; and, as a spark may kindle a great flame, so many might be defiled by one root of bitterness springing up to trouble them. The Apostle here refers to Deuteronomy 29:18, “ Lest there should be among you a root that beareth gall and wormwood,” and thereby many be defiled. In general, men do not perish alone in their iniquity; they infect others, and embolden them to transgress.