"Judge not, that you be not judged. For with the judgment you pronounce you will be judged, and the measure you give will be the measure you get. Why do you see the speck that is in your brother's eye, but do not notice the log that is in your own eye? Or how can you say to your brother, 'Let me take the speck out of your eye,' when there is the log in your own eye? You hypocrite, first take the log out of your own eye, and then you will see clearly to take the speck out of your brother's eye. Matthew 7:1–5 (RSV)
Luther observed that Scripture is the greatest of martyrs for people abuse and misuse it shamefully. Scripture is too often twisted in such a way to mean the opposite of what the text says.
'Judge not' is used by too many as an excuse or exemption of having their sin confronted. It is a means by which a pet sin can be kept instead of being confessed and repented. This popular way of deflecting any attention to a person's sin ignores the whole of Jesus' teaching.
We cannot begin to judge another unless we first judge ourselves. Who among us has so holy a life that we have nothing to confess and repent? How can I begin to judge another unless I have first taken the sin in my life seriously?
Yes, my neighbor may have a speck, a sin, in their lives. Unless I first have come to Christ seeking the forgiveness only He can give, the hypocrisy of my unconfessed sin will prevent the neighbor from seeing their sin.
Confessing and repenting, awash in the baptismal grace of Christ, I will be able in all charity and love to admonish my neighbor for the speck of sin in their life. Then, as a forgiven sinner, we can speak the Word of grace that sets us all free.