Jesus says in Matthew 7:1, “Do not judge, that you may not be judged.” From this statement one might conclude that judging is prohibited, but in the next verse the context helps us understand that the passage is not a prohibition. Rather it is a warning: “For in the way that you measure, it will be measured to you” (Matt. 7:2).
Luke 6:36-37 records a similar statement by Jesus: “Be merciful, just as your Father is merciful. And do not judge and you will not be judged, and do not condemn and you will not be condemned. Set free and you will be set free.”
The starting point here is following the Father’s example of mercy, and a sound standard of judgment. A few verses later, Jesus reminds His listeners to beware of the log that is in their own eye rather than trying to remove the speck from someone else’s eye. Read more about Are Christians Supposed to Judge Others?