Is celibacy essential to the Catholic priesthood?

**Question:** What are the theological (not practical) reasons for Catholic priests being celibate? In other words, is celibacy (or at least perpetual continence) essential to the Catholic priesthood? Note that I am not seeking for practical reasons like "If priests were not celibate they would have a harder time keeping a secret known trough confessions," etc. I am seeking for theological reasons (if they exist) that make celibacy fitting from the very notion of priesthood or something like that.