The concept of the Jubilee is a special year of remission of sins and universal pardon. In the Biblical book of Leviticus, a Jubilee year is mentioned to occur every fifty years, in which slaves and prisoners would be freed, debts would be forgiven and the mercies of God would be particularly manifest. In Christianity, the tradition dates to 1300, when Pope Boniface VIII convoked a holy year. Christian Jubilees, particularly in the Catholic tradition, generally involve pilgrimage to a sacred site, normally the city of Rome. At various times in Church history, they have been celebrated every 50 or 25 years.