The apostle reveals that our hope derives from our calling through the New Covenant and finds its ultimate source in God. Yet, God is more than the source of our hope: He is our hope. In verse 12, Isaiah refers to Him as the object of our hope. In Haggai 2:7, He is called "the Desire of All Nations," and in Romans 15:13, Paul calls Him "the God of hope," that is, hope's source.
Without God, we and this world have no hope except the normal desires common to the unconverted, things like filling our bellies, getting a good sleep, satisfying our eyes and ears, experiencing thrills and excitement, and accumulating money, power, and possessions. None of these is intrinsically evil, but God wants our hopes to be exceedingly higher. Verse 13 supplies a major condition to having this high quality of hope and thus the motivation it provides—believing. Remember, faith undergirds all the elements of motivation, and thus they clarify why living faith produces growth of fruit.
John W. Ritenbaugh
The Elements of Motivation (Part Three): Hope
Other Forerunner Commentary entries containing Romans 15:12: