God has always purpose that his people would worship and serve him not to get something but because they have received everything already.
Adam was to obey and worship because of the garden God has created for him.
And in this fallen state, we are not to obey and worship to try and earn salvation that we lost, but rather in response to the salvation that is already given.
Thus, works must always be done because of what God has already done, with gratitude in our hearts.
Since this is so fundamental, the temptation is always to change the motive for why we do works—to get something from God.
This undercuts the fuel or engine of our works and makes us run dry.
Thus, we need the gospel.
Like Job says we cannot add or take away from God—thus our obedience is in response to what God has added to us!
