Medieval Christians believed that all humans were tainted with the Original Sin: Adam and Eve's fall from God's grace. Salvation could be achieved by going through a three-part process: contrition, confession, and satisfaction. According to the source from Crossref (below), Medieval Christians had to repent for their sins and make confession to a priest, who would absolve the sinner of his or her sins. The priest might request the person to carry out other acts of penitence, including fasting, doing good works, or going on a pilgrimage. Some penitents were able to acquire what were called indulgences to be liberated from additional penance. The knights who fought in the Crusades were given indulgences, and, eventually, Medieval Christians were able to pay money for indulgences. Some indulgences wiped out all of one's sins, while others only removed part of them.