Matthew 7:1-5 “Judge not, that you be not judged. For with the judgment you pronounce you will be judged, and with the measure you use it will be measured to you. 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.
It means for example if you are an adulterer you cannot sit there and claim someone else is and not be judged for it as well. It is saying you must clear your own sin before judging someone else. This is because you will be judged accordingly.