Judge not, that ye be not judged.
For with what judgment ye judge, ye shall be judged: and with what measure ye mete, it shall be measured to you again.
And why beholdest thou the mote that is in thy brother's eye, but considerest not the beam that is in thine own eye?
Or how wilt thou say to thy brother, Let me pull out the mote out of thine eye; and, behold, a beam is in thine own eye?
Thou hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother's eye.
The moral lesson is to avoid hypocrisy and censoriousness. The analogy used is of a small object in another's eye as compared with a large beam of wood in one's own. The original Greek word translated as mote meant a stalk or twig rather than a tiny speck, as in modern usage. A proverb of this sort was familiar to the Jews and appears in numerous other cultures too. For example, the poet Robert Burns famously wrote:
Oh, wad some Power the giftie gie us,
To see ourselves as others see us!
The science fiction book The Mote in God's Eye takes its title from this passage, which it quotes in the foreword.