God himself, who is the Author of virtue, shall there be its reward; for, as there is nothing greater or better, he has promised himself. What else was meant by his word through the prophet, "I will be your God, and ye shall be my people," than, I shall be their satisfaction, I shall be all that men honourably desire - life, and health, and nourishment, and plenty, and glory, and honour, and peace, and all good things? This, too, is the right interpretation of the apostle, "That God may be all in all." He shall be the end of our desires who shall be seen without end, loved without cloy [disgust], praised without weariness.
From: The City Of God, trans. Marcus Dods (New York: Modern Library, 1950), 12.30.
If God contains the fullness of all good things in himself like an inexhaustible fountain, nothing beyond him is to be sought by those who strive after the highest good and all the elements of happiness . . . If the Lord will share his glory, power, and righteousness with the elect - nay, will give himself to be enjoyed by them and, what is more excellent, will somehow make them to become one with himself, let us remember that every sort of happiness is included under this benefit.
From: John Calvin, Institutes of the Christian Religion, ed. John T. McNeill, trans. Ford Lewis Battles (Philadelphia: Westminster, 1960), 3.25.10.
Clearly, then, nothing can satisfy man's will except such goodness, which is found, not in anything created, but in God alone. Everything created is a derivative good. He alone, who fills all good things thy desire [Ps. 102:5], can satisfy our will, and therefore in him alone our happiness lies.
From: St. Thomas Aquinas, Summa theologiae, trans. Thomas Gilby (New York: McGraw, 1969, 1a2ae; 2.8.
All quotations were taken from David Clyde Jones, Biblical Christian Ethics (Grand Rapids: Baker, 1994), 18-20.