Question:
Answer:
Jesus Christ, the great high priest of heaven (see Heb. 8:1-3), lived celibacy as a man and recommended celibacy for those who would serve him in the kingdom of God (Matt. 19:10-12). In addition, St. Paul, one of the earliest apostles, also extolled the virtues of celibacy, both for those devoted to serving the kingdom like himself and for Christians in general (1 Cor. 7:6, 32-40). So far from being invented in the Middle Ages, Christ exhorted the practice of celibacy in serving the kingdom and the early Church accordingly preached and practiced it.
Celibacy has long been allowed as a tradition in the East, of which the Syrian Orthodox and other Orthodox Churches have their ecclesiastical roots, though with certain provisions (e.g., no marriage after ordination and no married bishops). However, the Church’s disciplinary actions at the ecumenical councils of Lateran I and Lateran II in the 1100s were reforming disciplines re: priestly celibacy, not innovative ones.
For more on celibacy and the priesthood, see this historical overview posted on the Vatican website, our Catholic Answers tract and this article by Jason Evert.