A tax imposed in England and France, in 1188, by Pope Innocent III., to raise a fund for the crusade undertaken by Richard I. of England and Philip Augustus of France, against Saladin. sultan of Egypt, then going to besiege Jerusalem. By this tax every person who did not enter hlmself a crusader was obliged to pay a tenth of his yearly revenue and of the value of’all hls movables, except his wearing apparel, books, and arms. The Carthusians, Bemardines, and some other religious persons were exempt Gibbon remarks that when the necessity for this tax no longer existed, the church still clung to it as too lucrative to be abandoned, and thus arose the tithing of ecclesiastical benefices for the pope or other sovereigns. Enc. Lond
Source: Black's Law Dictionary 2nd Ed (1910)
