5 Great is the conflict which recluses undergo, and much their toil. But if any one compare their exertions with those which the right exercise of the Priesthood involves, he will find the difference as great as the distance between a king and a commoner. For there, if the labor is great indeed, yet the conflict is common to body and soul, or rather the greater part of it is accomplished by the condition of the body, and if this be not strong, the inclination remains undeveloped, and is unable to come out into action. For the habit of intense fasting, and sleeping on the ground, and keeping vigil, and refraining from the bath, and great toil, and all other means which they use for the affliction of the body are given up, when the body to be thus disciplined is not strong. But in this case purity of soul is the business in hand, and no bodily vigor is required to show its excellence. For what does strength of body contribute towards our being not self-willed, or proud, or headstrong, but sober and prudent, and orderly, and all else, wherein St. Paul filled up the picture of the perfect Priest? But no one could say this of the virtues of the recluse.
Source: On the Priesthood (New Advent)