If there is one phrase of any that is recognized as coming from the Bible, it is this: "Judge not that ye be not judged." But, the application of that phrase is varied, and possibly one of the least understood ideas.
Most commonly, we'll find people suggesting that this means, "don't condemn people so that you won't be condemned by God." In most cases, this is offered in the context of one person doing things that another believes to be morally wrong, and the other suggesting that maybe the first should mind their own business.
While there is precedent for this idea, it is not what the Messiah is saying in Matthew chapter 7.
First let's look at the word "not" in the phrase "judge not". The Greek word "may" simply suggests negative, not negation. The word "ook" or "ooh" means "no" or "don't", and the combination of the two, "ooh-may" means, "don't even think about it." Messiah is quoted as using the least powerful of these negatives, "may" when making this statement.
Now take a look at the word "judge". It is the word "kree-nos". Kree-nos doesn't mean condemn. That would be "kata-dikad-zo" or "kata-kree-nos" ("kata" means to lay down along side). "Kree-nos" is the Greek word from which we get the word "criteria". If it walks like a duck, quacks like a duck, swims like a duck; it's reasonable to conclude that we're talking about a duck. This is the word "kree-nos". It is fitting descriptive qualifications or standard to identify something.
The implication that God isn't going to judge us because we ignore the wrong doings of everyone else around us is a bit naive.
For it is written, As I live, saith the Lord, every knee shall bow to me, and every tongue shall confess to God. So then every one of us shall give account of himself to God.
"Kree-nos" isn't the condemnation, it is the standard by which someone is condemned or vindicated. Messiah is telling us not to set up our own arbitrary or artificial standard by which we compare others, or by which we compare ourselves.
He's talking about setting up heroes in our minds to which we are inclined to compare ourselves as well as villains by which we categorize others. He's saying, don't get caught up in that game of who you should be like, or who you think others should be like. He's telling us to live our own lives.
"Kree-nos" is a very important part of our lives. We have to have standards. We have to be able to diagnose between right and wrong. We we have to avoid is making up that standard on our own, or accepting the fluid cultural standard that is popular to the day.
Instead, we should do our best to apply God's Word to our own lives, and see His standard the goal that we strive toward: not condemning those who don't meet up to our level of achievement (because we all fall short of the goal); but pressing on in a positive direction.