But yet a third hold over fear and faith was wrought by the priesthood. Even as the priestly saying of Masses, bought at a price, was needed to keep the Christian safe in life, so the buying of Masses could hasten the release of his soul from purgatory after death. Purgatory was, to begin with, yet another pagan tenet, which in the first five centuries was regarded by the Church as heretical, though the text about "the spirits in prison" (1 Peter iii, 19; cp. 1 Cor. v, 5) gave colour to it, and Origen had entertained it. In all the writings of Ambrose it is not mentioned; Augustine treats it as dubious in despite of the authority of Origen; and the Eastern Church has never accepted the tenet. But in the writings of Gregory the Great it is treated as an established principle, with the economic corollary that he who would save himself or his kindred from prolonged pains in purgatory must lay out money on atoning Masses. Thus the whole cycle of real and supposed human experience was under the Church's sway, and at every stage on the course the pilgrim paid toll. The episodes of birth, marriage, and death were alike occasions for sacraments, each a source of clerical revenue; the fruits of the earth paid their annual tithe; and beyond death itself the Church sold privilege in the realm of shadows, winning by that traffic, perhaps, most wealth of all. It was a general corollary from the whole system that the Church had the right to grant "indulgences" for sin. If the Church could release from penalties in purgatory, it might grant pardons at will on earth. Such a doctrine was of course only very gradually evolved. First of all, perhaps again following a Manichæan precedent, the bishops individually began to waive canonical penances in consideration of the donation by offenders of sums of money for religious purposes. The principle is expressly laid down by Gregory I. There was at the outset no thought of selling the permission to commit an offence; the bishop merely used the opportunity of committed offences to enrich his church, very much as the law in so many cases inflicts fines instead of imprisonment. The procedure, too, was local and independent, even as that of abbots and monks who sold the privilege of seeing and kissing holy relics, which they often carried round the country in procession for revenue purposes. Only after such means of income had long been in use did the papacy attempt to monopolize the former, in virtue of its prerogative of "the keys." But step by step it absorbed the power to release from ordinary penances and to grant "plenary" remission from penances; and finally it undertook, what the bishops had never ventured on, to remit the penalties of purgatory in advance. Such enterprise was evoked only by a great occasion--the Crusades.