The path of faith is constantly beset with dangers and every believer needs to be so careful. Each man must watch himself, of course, but the application here may be broader than that. It may be that each of us should watch with care for others. The word rendered “looking diligently,” is the same word as is used by Peter in relation to overseers in 1 Peter 5:2, “taking the oversight.” Perhaps, there is a responsibility, which delegates to all of us the responsibility to care for one another. We are so dependent upon the grace of God for the maintaining of the holiness that we desire. So, while pursuing peace and holiness we must always be looking carefully, watching diligently, lest any should fail of that grace. Nothing robs a person of that grace like a root of bitterness; a root producing bitter leaves and poisonous fruit. A root of bitterness is a contaminating, corrupting element to be prevented at all cost, or to be seriously dealt with when it appears.