[Christians are] not to be hasty in making negative judgments on their fellows. It is a dangerous procedure because it invites a similar judgment in return. And it is a difficult procedure because our own faults make it hard for us to see precisely what is amiss in our fellows. Jesus is not, of course, forbidding all judgments; He is warning against the hasty condemnations that are so easy to make, and so characteristic of the human race.
Leon Morris