"Who then can pride himself over against someone else and claim to be better than he? Especially in view of the fact that he is always capable of doing exactly the same as the other does and, indeed, that he does secretly in his heart before God what the other does openly before men. And so we must never despise anyone who sins but must generously bear with him as a companion in a common misery. We must help one another just as two people caught in the same swamp assist each other. Thus we must 'bear one another's burdens and fulfill the law of Christ' (Galatians 6:2). But if we despise the other, we shall both perish in the same swamp."
Martin Luther, Lectures on Romans, page 115.