Pope Paul VI
Sacerdotalis Caelibatus §75
Sacerdotalis Caelibatus: On the Celibacy of the Priest
75 The priest should apply himself above all else to developing, with all the love grace inspires in him, his close relationship with Christ, and exploring this inexhaustible and enriching mystery; he should also acquire an ever deeper sense of the mystery of the Church. There would be the risk of his state of life seeming unreasonable and unfounded if it is viewed apart from this mystery. Priestly piety, nourished at the table of God's word and the Holy Eucharist, lived within the cycle of the liturgical year, inspired by a warm and enlightened devotion to the Virgin Mother of the supreme and eternal High Priest and Queen of the Apostles, (122) will bring him to the source of a true spiritual life which alone provides a solid foundation for the observance of celibacy.
Source: Sacerdotalis Caelibatus (Vatican.va)