Ante-Nicene Fathers, Vol III:
Tertullian: Part III: Chapter III.

Chapter III.

Grant now, O blessed, that even to Christians the prison is unpleasant; yet we were called to the warfare of the living God in our very response to the sacramental words. Well, no soldier comes out to the campaign laden with luxuries, nor does he go to action from his comfortable chamber, but from the light and narrow tent, where every kind of hardness, roughness and unpleasantness must be put up with. Even in peace soldiers inure themselves to war by toils and inconveniences—marching in arms, running over the plain, working at the ditch, making the testudo, engaging in many arduous labours. The sweat of the brow is on everything, that bodies and minds may not shrink at having to pass from shade to sunshine, from sunshine to icy cold, from the robe of peace to the coat of mail, from silence to clamour, from quiet to tumult. In like manner, O blessed ones, count whatever is hard in this lot of yours as a discipline of your powers of mind and body.  You are about to pass through a noble struggle, in which the living God acts the part of superintendent, in which the Holy Ghost is your trainer, in which the prize is an eternal crown of angelic essence, citizenship in the heavens, glory everlasting. Therefore your Master, Jesus Christ, who has anointed you with His Spirit, and led you forth to the arena, has seen it good, before the day of conflict, to take you from a condition more pleasant in itself, and has imposed on you a harder treatment, that your strength might be the greater. For the athletes, too, are set apart to a more stringent discipline, that they may have their physical powers built up. They are kept from luxury, from daintier meats, from more pleasant drinks; they are pressed, racked, worn out; the harder their labours in the preparatory training, the stronger is the hope of victory. “And they,” says the apostle, “that they may obtain a corruptible crown.” 8966 We, with the crown eternal in our eye, look upon the prison as our training-ground, that at the goal of final judgment we may be brought forth well disciplined by many a trial; since virtue is built up by hardships, as by voluptuous indulgence it is overthrown.

Footnotes

1 Cor. ix. 25.