Cyril of Alexandria — as excerpted in the Catena Aurea on Luke 6:39-42

“The Lord added to what had gone before a very necessary parable, as it is said, And he spake a parable to them, for His disciples were the future teachers of the world, and it therefore became them to know the way of a virtuous life, having their minds illuminated as it were by a divine brightness, that they should not be blind leaders of the blind. And then he adds, Can the blind lead the blind? But if any should chance to attain unto an equal degree of virtue with their teachers, let them stand in the measure of their teachers, and follow their footsteps. Hence it follows, The disciple is not above his master. Hence also Paul says, Be ye also followers of me, as I am of Christ (1 Cor. 1:11.). Since Christ therefore judged not, why judgest thou? for He came not to judge the world, but to shew mercy.”