Edward Gibbon, The Decline and Fall of the Roman Empire, Chp. VIII Part II

Every mode of religion, to make a deep and lasting impression on the human mind, must exercise our obedience, by enjoining practices of devotion, for which we can assign no reason; and must acquire our esteem, by inculcating moral duties analogous to the dictates of our own hearts. The religion of Zoroaster was abundantly provided with the former and possessed a sufficient portion of the latter. At the age of puberty, the faithful Persian was invested with a mysterious girdle, the badge of the divine protection; and from that moment all the actions of his life, even the most indifferent, or the most necessary, were sanctified by their peculiar prayers, ejaculations, or genuflections; the omission of which, under any circumstances, was a grievous sin, not inferior in guilt to the violation of the moral duties. The moral duties, however, of justice, mercy, liberality, &c., were in their turn required of the disciple of Zoroaster, who wished to escape the persecution of Ahriman, and to live with Ormusd in a blissful eternity, where the degree of felicity will be exactly proportioned to the degree of virtue and piety.