At the conclusion of his treatise on The Life of Moses, Gregory of Nyssa wrote:
These things concerning the perfection of the virtuous life, O Caesarius, man of God, we have briefly written for you, tracing in outline like a pattern of beauty the life of the great Moses, so that each one of us might copy the image of the beauty which has been shown to us by imitating his way of life. What more trustworthy witness of the fact that Moses did attain the perfection which was possible would be found than the divine voice which said to him: “I have known you more than all others” [Exod. 33:17, 12]? It is also shown in the fact that he is named the “friend of God” [33:11] by God himself, and by preferring to perish with all the rest if the Divine One did not through his goodwill forgive their errors, he stayed God’s wrath against the Israelites. God averted judgment so as not to grieve his friend. All such things are a clear testimony and demonstration of the fact that the life of Moses did ascend the highest mount of perfection.
Since the goal of the virtuous way of life was the very thing we have been seeking, and this goal has been found in what we have said, it is time for you, noble friend, to look to that example and, by transferring to your own life what is contemplated through spiritual interpretation of the things spoken literally, to be known by God and to become his friend. This is true perfection: not to avoid a wicked life because, like slaves, we servilely fear punishment, nor to do good because we hope for rewards, as if cashing in on the virtuous life by some businesslike and contractual arrangement. On the contrary, disregarding all those things for which we hope and which have been reserved by promise, we regard falling from God’s friendship as the only thing dreadful, and we consider becoming God’s friend the only thing worthy of honor and desire. This, as I have said, is the perfection of life.
Gregory of Nyssa: The Life of Moses, trans. Abraham J. Malherbe and Everett Ferguson (pp. 131-132).