The following selection from Calvin’s Institutes suggests his preference for gratitude as a motivation for obedience – he also seems to ground obedience in Divine Command Theory. Context is also key as he is opposing those who would ground godliness in the desire for reward as preeminent. John Piper has warned against the danger of grounding obedience in gratitude as if one was “returning favors” (link).
At present, let it be sufficient merely to advert to the weakness of their objection. This may be done in two ways.  For, first, they are altogether in error when they say that, unless a hope of reward is held forth, no regard will be had to the right conduct of life. For if all that men do when they serve God is to look to the reward, and hire out or sell their labour to him, little is gained: he desires to be freely worshipped, freely loved: I say he approves the worshipper who, even if all hope of reward were cut off, would cease not to worship him. Moreover, when men are to be urged, there cannot be a stronger stimulus than that derived from the end of our redemption and calling, such as the word of God employs when it says, that it were the height of impiety and ingratitude not to “love him who first loved us;” that by “the blood of Christ” our conscience is purged “from dead works to serve the living God;” that it were impious sacrilege in any one to count “the blood of the covenant, wherewith he was sanctified, an unholy thing;” that we have been “delivered out of the hands of our enemies,” that we “might serve him without fear, in holiness and righteousness before him, all the days of our life;”
© 2012, Rick Hogaboam. All rights reserved.