„What is a charitable heart? It is a heart which is burning with love for the whole creation, for men, for the birds, for the beasts … for all creatures. He who has such a heart cannot see or call to mind a creature without his eyes being filled with tears by reason of the immense compassion which seizes his heart; a heart which 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. That is why such a man never ceases to pray for the animals … [He is] … moved by the infinite pity which reigns in the hearts of those who are becoming united with God.“
— Isaac of Nineveh
Mystic Treatises, cited in Vladimir Lossky, The Mystical Theology of the Eastern Church (1976), [//books.google.it/books?id=dxqvWwPSCSwC&pg=PA111 p. 111]; also cited and discussed in A. M. Allchin, The World is a Wedding (1978), p. 85. Quoted in Andrew Linzey, Animal Theology (1994), [//books.google.it/books?id=ESTjQYS_8hMC&pg=PA56 p. 56].