They say that Abba Macarius the Egyptian [St. Macarius the Great] on one occasion went up from Scete to the Nitrian mountain, and as he drew near to a certain place, he said to his disciple, "Pass on a little in front of me"; and when he had done so there met him a certain heathen priest, who was running along and carrying some wood about the time of noon. And that brother cried out to him and said, "O minister to devils, where run thou?"  And the priest turned round and smote him with many severe blows, and he left him with but very little breath remaining in him, and he took up his wood and went on his way; and when he had gone on a little further the blessed Macarius met him on his journey, and said to him, "May you be helped, O man of labours?"  And the priest was astonished, and came to him and said, "What fair thing have you seen in me that you should salute me [in this gracious fashion] ?"  And the old man said to him, "I see that you toil, and that you do not know that you are toiling for naught"; then he said to the old man, "At your salutation I also was very sorry, and I learned that you did belong to the Great God. But a wicked monk met me just before you didst, and he cursed me, and I smote him even to death."  And the old man knew that it was his disciple [of whom he spake], and the priest laid hold upon the feet of Macarius, and said to him, "I will not let you [go] until you make me a monk"; and they came to the place where the brother was lying, and they carried him and brought him to the church of the mountain. Now when the fathers saw the heathen priest with him, they marvelled that he had been converted from the error which he had held; and Macarius took him and made him a monk, and through him many of the heathen became Christians. And Abba Macarius said, " ' An evil word makes wicked even those who are good, and a good word makes good even those who are wicked,' as it is written."

from Sayings of the Holy Desert Fathers

God is loving to man, and loving in no small measure. For say not, I have committed fornication and adultery: I have done dreadful things, and not once only, but often: will He forgive? Will He grant pardon? Hear what the Psalmist says: "How great is the multitude of Your goodness, O Lord!" 

Your accumulated offenses surpass not the multitude of God’s mercies: your wounds surpass not the great Physician’s skill. Only give yourself up in faith: tell the Physician your ailment: say thou also, like David: "I said, I will confess me my sin unto the Lord": and the same shall be done in your case, which he says immediately: "And you forgave the wickedness of my heart.”

St. Cyril of Jerusalem

And pray without ceasing in behalf of other men. For there is in them hope of repentance that they may attain to God. See, then, that they be instructed by your works, if in no other way. Be meek in response to their wrath, humble in opposition to their boasting: to their blasphemies return your prayers; in contrast to their error, be steadfast in the faith; and for their cruelty, manifest your gentleness.

St Ignatius of Antioch

It is required that not only with the body should we fast, but with the soul. Now the soul is humbled when it does not follow wicked opinions, but feeds on becoming virtues. For virtues and vices are the food of the soul, and it can eat either of these two. Bend your appetite toward virtues, as Paul says, "Being nourished by the word of truth."

St. Athanasios of Alexandria