Who told Christians their sins would be forgiven if they fought in the crusades?

Pope Urban II is credited with encouraging Christians to join the Crusades and promising them forgiveness of sins. During the Council of Clermont in 1095, he called for a military expedition to the Holy Land and offered spiritual rewards, including indulgences, to those who participated in the crusade. This promise was a significant motivator for many to take up arms in the name of their faith.