Don't judge, so that you won't be judged. For with whatever judgment you judge, you will be judged; and with whatever measure you measure, it will be measured to you. (Matthew 7:1-2)
The first portion of these verses is one of those passages of Scripture that we must be careful not to strain beyond its proper meaning. It is frequently abused and misapplied by the enemies of true religion. It is possible to press the words of the Bible so far that they yield not medicine, but poison.
Our Lord does not mean that it is wrong, under any circumstances, to pass an unfavorable judgment on the conduct and opinions of others. We should have decided opinions. We are to "prove all things." We are to "try the spirits." Nor does He mean that it is wrong to reprove the sins and faults of others unless we are perfect and faultless ourselves. Such an interpretation would contradict other parts of Scripture. It would make it impossible to condemn error and false doctrine. It would bar anyone from attempting the office of a minister or a judge.
What our Lord means to condemn is a censorious and fault-finding spirit: a readiness to blame others for trifling offenses or matters of indifference - a habit of passing rash and hasty judgments - a disposition to magnify the errors and infirmities of our neighbors and make the worst of them. This is what our Lord forbids. It was common among the Pharisees. It has always been common from their day down to the present time. We must all watch against it. We should "believe all things" and "hope all things" about others and be very slow to find fault. This is Christian charity (1 Corinthians 13:7).
Adapted from The Gospel of Matthew by J.C. Ryle (Chapter 7).