A great elder was living in Syria around the boundaries of Antiochia and he had a brother who was ready to judge if he saw a brother committing a mistake.
Many times the elder taught him saying :
`Indeed my son you are in the wrong and you lose your soul as long as nobody knows what`s in the man, only the spirit that`s in him. Many times they do bad deeds in front of people and in secret they repent before God. We see the sin but the repentance and the good deeds are known only by God.
For this reason even if you saw with your own eyes a man sinning, do not judge him at all, for only God is a Judge. Any man who judges someone else is like an antichrist for Christ, as long as he took away from Him the rule and reign given by the Father, making himself a judge in His place.
Excerpt from the Egyptian Patericon.