What does the passage say?
1“Judge not, that you be not judged.
2For with what judgment you judge, you will be judged; and with the measure you use, it will be measured back to you.
3And why do you look at the speck in your brother’s eye, but do not consider the plank in your own eye?
4Or how can you say to your brother, ‘Let me remove the speck from your eye’; and look, a plank is in your own eye?
5Hypocrite! First remove the plank from your own eye, and then you will see clearly to remove the speck from your brother’s eye.
These words come from the Sermon on the Mount, Matthew 5 to 7, spoken to Jesus' disciples with the crowds listening. The picture is meant to be almost comic: a person with a plank in their eye offering to remove a speck from someone else's. Look at the end of verse 5. Jesus still expects the speck to come out, once the plank has.
Does Jesus ask His followers to discern?
15“Beware of false prophets, who come to you in sheep’s clothing, but inwardly they are ravenous wolves.
16You will know them by their fruits. Do men gather grapes from thornbushes or figs from thistles?
Ten verses later, Jesus tells the same hearers to watch for false prophets and to know them by their fruits. That takes a kind of judgment. In John's Gospel He puts it plainly:
Do not judge according to appearance, but judge with righteous judgment.”
Where do Christians disagree?
Christians differ over when to speak about another person's choices, how to do it and who should. The passage gives an order that applies to everyone. Look at yourself first. Measure others the way you would want to be measured. Aim to help, not to condemn.
For example: “Lord, show me the plank in my own eye before I point at anyone else. Make me honest about myself, and gentle when I need to speak. Amen.” This is a prepared example.
For a method you can use with any verse, read how to read a Bible verse in context. For the whole book, see our guide to Matthew.