Macarius of Egypt (AD 4th-5th century), (attributed), Hom. 14: PG 34, 569-573
Macarius was abbot of a community of cenobites and a monk of great spiritual stature and authority. The best known of his works are Fifty Spiritual Homilies.
What he discusses here is much the reason I've never found the late Walter Kaufmann's argument against Christian morality very compelling. Kaufmann, a premier Nietzsche scholar, argues that Christian morality is deficient because it rests on moral recompense. True virtue, he says, seeks not reward but does what is right for the sheer fact that it is right. The so to speak "fallacy of reward" Kaufmann finds fault with in Christianity is, in his eyes, but the flispide of a morality based on doing good to avoid punishment.
But I've never thought Kaufmann was anywhere near a substantive critique on this point. I think it must be due to a misunderstanding on his part of what Christian reward is about. The reward a Christian seeks is not, as in Islam, a matter of celestial goodies, but is rather a matter of knowing God fully and directly, some might even say "in His essence." Every moral effort of faith by a Christian aims at pleasing God not for the "reward" of someting else, but, quite simply, for the prize of *knowing God*. The reward of Heaven is the reward of life with God. And insofar as God is, among other things, Goodness itself, the Christian desire for Him in "faith working in love" is a desire for goodness itself.
Hence, Christian virtue does not seek a greater good (ie., reward) for doing lesser goods (i.e., virtuous acts). Rather, the exercise of virtue is reward in and of itself because it partakes of, and unites us with, God. Beyond that, I think Kaufmann misses the elemental truth that there is an intrinsic "reward" in every act of virtue. Virtue is always rewarding for the sheer fact that virtue is *good*. Being virtuous *is* the reward of being virtuous. Macarius is wise to look at the farmer: a farmer is "rewarded" for his farming only in the merely instrumental sense that the farming is not complete until it produces a harvest. As in farming, so in morality: the "harvest" is an inextricable part of the teleological riches of life. It is an ineluctable moral fact that, once we understand what goodness is, doing good will seem like a reward, even apart from an eschatological remuneration from God.