The second prescriptive [of the WSC, viz. to enjoy God forever] is entirely scriptural. To redeemed human beings, glorifying God is a delight. In chapter 16, I showed how often Scripture mentions the rewards that God has promised to those who love him. Those rewards are delightful beyond our imagining, and they are a powerful motivation to obedience. In that chapter, I emphasized, that the Christian ethic is far removed from Kantian deontology, in which we do our duty for duty’s sake, with no thought of reward. Rather, in the Christian life, we seek to do God’s will for God’s rewards.
John Frame, Doctrine of the Christian Life, 304.
Here are Frame’s comments from Chapter 16:
God promises rewards to his people, and they receive those rewards when Jesus returns. That promise serves as an additional motivation (Ps. 19:11; Matt. 5:12, 46; 6:1-6; 10:41-42; Rom 14:10; 1 Cor. 3:8-15; 9:17-25; 2 Cor. 5:10; Eph. 6:7-8; Col. 3:23-25; 2 Tim. 4:8; 1 Peter 5:4; James 1:12; 2 John 8; Rev. 11:18).
I confess that I was surprised by the number of times Scripture uses rewards to motivate obedience. Like many of us, I tend toward the Kantian notion that we should simply do our duty for duty’s sake and never think about reward. But that notion is quite unbiblical. If God takes the trouble (this many times!) to urge our obedience by a promise of reward, we should embrace that promise with thanks, not despise it. That is, we should not only do good works, but we should do them for this reason.
This teaching, of course, is not salvation by works or merit. Although the word reward is used in these passages, there is no suggestion that we have earned the reward in the sense that we have paid God what the reward is worth. Jesus says that even when we have done everything commanded of us (and not one of us has done that), we have none no more than our duty (Luke 17:7-10). Indeed, in that case we are ‘unworthy’ servants. Elsewhere, Scripture represents the reward as something out of all proportion to the service rendered (Matt. 19:29; 20:1-16; 24:45-47; 25:21-30; Luke 7:36-50; 12:37).
Nevertheless, there is some sort of gradation in the rewards given to individuals. . . . The parable of the talents (Matt. 25:14-30; cf. Luke 19:11-27) provides the best argument for proportionate rewards. One cannot argue, however, that the degree of investment success ascribed to the first two servants entitles them, as a strict payment, to the master’s rewards. Rather, the master acts generously, out of the goodness of his heart. This is to say that here, as with every transaction we have with God, we deal with him as a person, not with an impersonal principle of cause and effect.
Essentially, the reward is the kingdom itself (Matt. 5:3, 10; 25:34), which comes by electing grace (Matt. 25:34; Luke 12:31-32). Good works follow, rather than precede, this gift (Luke 12:33-48). TO put it differently, the Lord himself is the inheritance of his people (Pss. 16:5; 73:24-26; Lam. 3:24). He is the inheritance of every believer. If there are differences of degree, they are differences of intimacy with the Lord himself. If some glorified saints lie closer than others to God’s heart, no one else will be jealous or angry, for the eternal kingdom excludes such emotions. Rather, the lesser members of that kingdom will rejoice t the greater blessings given to others, and those who are greatest will serve the lesser—beginning with the Lord himself [Luke 12:37] . . . . Who would not want as much intimacy as possible with such a wonderful Lord? Here is a reward that profoundly motivates holiness of heart and life.
John Frame, Doctrine of the Christian Life, 283-85.