Mark the blameless man, and observe the upright; the future of that man is peace. (Psalm 37:37)
It is one thing to mark a person; it is another to judge him or her. All we can do is judge actions and deeds. We cannot judge the one doing them. Always remember, there will be at least one thing you do not know about any given situation. Therefore, let us mark those people who are doing the will of the Lord and prospering at His will. Let us follow their example of faithfulness, diligence and patience. Likewise, let us mark those who are rebellious, unfaithful and lazy. Let us not follow their example, but let us learn to avoid their lifestyles. Love them, but mark them. There ought to be people in your life that are marked fallow and there ought to be people marked avoid. Naturally, there should be more than these two categories. You may wish to include marking people to help or mentor or lead to Christ. Marking is not to be and should not be confused with judging.