6 The close relationship that the Fathers of the Church and ecclesiastical writers established over the centuries between the ministering priesthood and celibacy has its origin partly in a mentality and partly in historical circumstances far different from ours. In patristic texts we more frequently find exhortations to the clergy to abstain from marital relations rather than to observe celibacy; and the reasons justifying the perfect chastity of the Church's ministers seem often to be based on an overly pessimistic view of man's earthly condition or on a certain notion of the purity necessary for contact with sacred things. In addition, it is said that the old arguments no longer are in harmony with the different social and cultural milieus in which the Church today, through her priests, is called upon to work.
Source: Sacerdotalis Caelibatus (Vatican.va)