Why do you obey God? If it is out of a sense of gratitude, it may indeed be off base. For example, “Look how much God has done for you. Shouldn’t you, out of gratitude, do much for him?” Or, “You owe God everything that you are and have. What have you done for him in return?”
There are 3 problems with this:
1. First, it is impossible to pay God back for all the grace he has given us. (Romans 11:35). He already owns all we have to give him — including all our efforts.
2. Even if we succeeded in paying him back for all his grace to us, it would only be turning grace into a business transaction. If we can pay him back, it was not grace. If someone tries to show you a special favor of love by having you over for dinner, and you end the evening by saying that you will pay them back by having them over next week, you nullify their grace and turn it into a trade. God does not like to have his grace nullified. He likes to have it glorified (Ephesians 1:6, 12, 14).
3. It tends to overlook the crucial importance of having faith in God’s future grace. Gratitude looks back to grace received in the past and feels thankful. Faith looks forward to grace promised in the future — whether in five minutes or five centuries from now — and feels hopeful. “Faith is the assurance of things hoped for” (Hebrews 11:1).

Obedience does not consist in paying God back and therefore turning grace into a trade. Obedience comes from trusting in God for more grace — future grace — and thus magnifying the infinite resources of God’s love and power. Faith looks to the promise, I will be “with you wherever you go” (Joshua 1:9), and goes ahead, in obedience to whatever He asks you to do.
~ John Piper