"For the life of the flesh is common to both men and animals, whereas the life of the spirit is possessed only by the pure in heart ..."

"In every age and century, the purpose of the Prophets of God and their chosen ones hath been no other but to affirm the spiritual significance of the terms “life,” “resurrection,” and “judgment.” If one will ponder but for a while this utterance of ‘Alí in his heart, one will surely discover all mysteries hidden in the terms “grave,” “tomb,” “ṣiraṭ,” “paradise” and “hell.” But oh! how strange and pitiful! Behold, all the people are imprisoned within the tomb of self, and lie buried beneath the nethermost depths of worldly desire! Wert thou to attain to but a dewdrop of the crystal waters of divine knowledge, thou wouldst readily realize that true life is not the life of the flesh but the life of the spirit. For the life of the flesh is common to both men and animals, whereas the life of the spirit is possessed only by the pure in heart who have quaffed from the ocean of faith and partaken of the fruit of certitude. This life knoweth no death, and this existence is crowned by immortality. Even as it hath been said: “He who is a true believer liveth both in this world and in the world to come.”"

-Bahá'u'lláh, The Kitáb-i-Íqán , p. 120