43 But the Christian priesthood, being much superior to that of the Old Law, demanded a still greater purity. The law of ecclesiastical celibacy, whose first written traces pre-suppose a still earlier unwritten practice, dates back to a canon of the Council of Elvira, at the beginning of the fourth century, when persecution still raged. This law only makes obligatory what might in any case almost be termed a moral exigency that springs from the Gospel and the Apostolic preaching. For the Divine Master showed such high esteem for chastity, and exalted it as something beyond the common power; He Himself was the Son of a Virgin Mother, Florem Matris Virginis , and was brought up in the virgin family of Joseph and Mary; He showed special love for pure souls such as the two Johns - the Baptist and the Evangelist. The great Apostle Paul, faithful interpreter of the New Law and of the mind of Christ, preached the inestimable value of virginity, in view of a more fervent service of God, and gave the reason when he said: "He that is without a wife is solicitous for the things that belong to the Lord, how he may please God." All this had almost inevitable consequences: the priests of the New Law felt the heavenly attraction of this chosen virtue; they sought to be of the number of those "to whom it is given to take this word," and they spontaneously bound themselves to its observance. Soon it came about that the practice, in the Latin Church, received the sanction of ecclesiastical law. The Second Council of Carthage at the end of the fourth century declared: "What the Apostles taught, and the early Church preserved, let us too, observe."
Source: Ad Catholici Sacerdotii (Vatican.va)