Saint Dismas

Have you no fear of God, for you are subject to the same condemnation. And indeed, we have been condemned justly, for the sentence we received corresponds to our crimes, but this man has done nothing criminal. Jesus, remember me when you come into your kingdom.

-- Saint Dismas from Luke 23: 40 - 42

Saint Maximus the Confessor

To harbor no envy, no anger, no resentment against an offender is still not to have charity for him. It is possible, without any charity, to avoid rendering evil for evil. But to render, spontaneously, good for evil - such belongs to a perfect spiritual love. 

-- Saint Maximus the Confessor

Saint Augustine of Hippo

Whoever, then, loves his neighbor aright, ought to urge upon him that he too should love God with his whole heart, and soul, and mind. For in this way, loving his neighbor as himself, a man turns the whole current of his love both for himself and his neighbor into the channel of the love of God, which suffers no stream to be drawn off from itself by whose diversion its own volume would be diminished. 

-- Saint Augustine of Hippo

Saint Serapion the Scholastic

The mind is purified by spiritual knowledge (or by holy meditation and prayer), the spiritual passions of the soul by charity, and the irregular appetites by abstinence and penance.

-- Saint Serapion the Scholastic