A heart full of sorrow on account of its feebleness and impotence regarding outward physical deeds takes the place of all physical works. Deeds of the body performed without sorrow of mind are like a body without a soul. The man who is sorely grieved in his heart but gives rein to his senses, is like a sick man who suffers physically but who opens his mouth to every kind of harmful food. The man who is sorely grieved in his heart but gives rein to his senses is like a man with an only son, whom he slaughters with his own hands, little by little. Sorrow of mind is a precious gift before God; and the man who bears this gift as he ought is like a man who bears holiness in his members. A man who unleashes his tongue against other men for good or evil is unworthy of this grace. …
Mercy and justice in one soul is like a man who worships God and the idols in one house. Mercy is opposed to justice. Justice is the equality of the even scale, for it gives to each as he deserves; and when it makes recompense, it does not incline to one side or show respect of persons. Mercy, on the other hand, is a sorrow and pity stirred up by goodness, and it compassionately inclines a man in the direction of all; it does not requite a man who is deserving of evil, and to him who is deserving of good it gives a double portion. If, therefore, it is evident that mercy belongs to the portion of righteousness, then justice belongs to the portion of wickedness. As grass and fire cannot coexist in one place, so justice and mercy cannot abide in one soul. As a grain of sand cannot counterbalance a great quantity of gold, so in comparison God’s use of justice cannot counterbalance His mercy.
As a handful of sand thrown into the great sea, so are the sins of all flesh in comparison with the mind of God. And just as a strongly flowing spring is not obstructed by a handful of dust, so the mercy of the Creator is not stemmed by the vices of His creatures. As a man who sows in the sea and expects to reap a harvest, so is he who remembers wrongs and prays. As the flame of fire cannot be checked from rising upward, so the prayers of the merciful are not hindered from ascending to Heaven. The current of a stream runs swiftly in a narrow place, and likewise the force of anger whenever it finds a place in our mind. The man who has acquired humility in his heart is dead to this world. He who is dead to the world has died to the passions. For to the man who has died in his heart to his kinsmen, the devil is dead. He who has found malice, with it has found him who originally found it.
The Ascetical Homilies of Saint Isaac the Syrian, I, 51, translated by the Holy Transfiguration Monastery, Boston, 1984. 243-244.