What is a charitable heart? It is a heart that is burning with charity for the whole of creation, for men, for the birds, for the beasts, for the demons - for all creatures. He who has such a heart cannot see or call to mind a creature without his eyes becoming filled with tears by reason of the immense compassion that seizes his heart, a heart that is softened and can no longer bear to see or learn from others of any suffering, even the smallest pain, being inflicted upon a creature. This is why such a man never ceases to pray also for the animals, for the enemies of Truth, and for those who do him evil, that they may be preserved and purified. He will pray even for the reptiles, moved by the infinite pity that reigns in the hearts of those who are becoming united to God.

(Saint Isaac the Syrian)