Basil the Great
Catena Aurea · Lukasevangelium 6
And he spake a parable unto them, Can the blind lead the blind? shall they not both fall into the ditch? The disciple is not above his master: but every one that is perfect shall be as his master. And why beholdest thou the mote that is in thy brother’s eye, but perceivest not the beam that is in thine own eye? Either how canst thou say to thy brother, Brother, let me pull out the mote that is in thine eye, when thou thyself beholdest not the beam that is in thine own eye? Thou hypocrite, cast out first the beam out of thine own eye, and then shalt thou see clearly to pull out the mote that is in thy brother’s eye.
(Hom. 9, in Hexameron.) In truth, self knowledge seems the most important of all. For not only the eye, looking at outward things, fails to exercise its sight upon itself, but our understanding also, though very quick in apprehending the sin of another, is slow to perceive its own defects.