Verse one of this chapter is a "famous verse" among many Christians, "Judge not..."! We love to use that phrase with anyone who even seems close to passing some kind of criticism against us. But, do we really pay attention to all that Jesus is saying? You see, the very next verse seems to contradict the previous verse. If we are not to judge, period, then why did Jesus bring up the matter of judging in verses 2-5 in a cautionary way? Consider these thoughts, please:
Verse one speaks of unfair and unrighteous judgment, the kind of judgment where one is presupposing to know the motivation and plan of the other person's actions. Its the kind of judgment that is unfair, ignorant, and many times, spiteful. When someone "guesses" as to why you're doing something and then criticizes you, that is unfair and unholy judgment. They should recognize that they don't know all the facts and, therefore, should be quiet as to why you do what you do.
On the other hand, verses 2-5 seem to indicate a kind of judgment that isn't being unfair or without knowledge. Its the kind of judgment where, if you do discern something is wrong in the behavior of someone else, you can constructively criticize the other person knowing full well that they have the right to do the same to you. "Judge not, less you be judged" is saying don't criticize someone and not expect to have the same thing done to you. And if you should say something out of genuine friendship and concern for someone else then you shouldn't be offended if they do the same for you out of their genuine friendship and concern.
I'll add more to this tomorrow.