Question   What is the sign that a man has attained to purity of heart, and when does a man know that his heart has entered into purity?

Answer   When he sees all men as good and none appears to him to be unclean and defiled, then in very truth is his heart pure. For how could anyone fulfill the word of the Apostle, that ‘A man should esteem all better than himself’ with a sincere heart, if he does not attain to the saying, ‘A good eye will not see evil’?

St. Isaac the Syrian,The Ascetical Homilies of Saint Isaac the Syrian (I, 37), translated by the Holy Transfiguration Monastery, Boston, 1984. p. 177.