Let there always be a preponderance of mercy with you, even though you don't feel such mercy in yourself, as God has for the world ... A cruel and merciless heart is never purified. A merciful man is the doctor of his own soul, because as it were a by a strong wind from is heart he drives out the darkness of the passions.
Isaac of NinevehThe beginning of divine wisdom is clemency and gentleness, which arise from greatness of soul and the bearing of infirmities.
Isaac of NinevehLove sinners, but hate their deeds, and do not disdain sinners for their failings, so that you yourself do not fall into the temptation in which they abide... Do not be angry at anyone and do not hate anyone, neither for their faith, nor for their shameful deeds... Do not foster hatred for the sinner, for we are all guilty... Hate his sins, and pray for him, so that you may be made like unto Christ, who had no dislike for sinners, but prayed for them.
Isaac of NinevehThe man who follows Christ in solitary mourning is greater than he who praises Christ amid the congregation of men.
Isaac of NinevehWhen you want to direct someone toward the good, first put him at peace bodily and honor him with words of love. For nothing inclines such a man to shame and induces him to cast of his vice and be changed for the better as do bodily goods and honor, which he sees in you. Then, with love tell him a word or two, and do not be inflamed with anger toward him. Do not let him see any cause of enmity toward you. For love does not know how to lose its temper.
Isaac of Nineveh