[metmom]

Discipline is always based on doctrine. Discipline that is not necessitated by doctrine is a mere imposition. (And the Church is vigilant not to impose disciplines on the faithful that are not logically necessitated by doctrine.)

So what doctrine mandates celibacy for the priesthood, the forbidding of priests to marry, or making them leave the priesthood if they do, or prohibiting married men from becoming priests unless they're transplants from other denominations?

[Arthur McGowan]

The Eucharist makes present THE nuptial act (Christ’s crucifixion and death) that unites Christ and his bride, the Church.

Starting within the lifetimes of the apostles, the conviction began, and grew, that the role of the priest in celebrating the Eucharist required perfect and perpetual continence of the priest.

[Arthur McGowan]

This is excellent:

http://www.unamsanctamcatholicam.com/history/79-history/465-celibacy-in-the-early-church.html