Richard Sibbes (1577-1635), Puritan pastor and author (on whom Mark Dever did his doctorate), writes this in Glorious Freedom, which is a book-length exposition of 2 Cor 3:18:
"When we are drawn to duties out of wrong motives or fear or custom, and not from a new nature, this is not from the Spirit, and their performance is not from the true liberty of the Spirit. For under the liberty of the Spirit, actions come off naturally, not forced by fear or hope or any extra motives. A child does not need other motives to please his father. When he knows he is the child of a loving father, it is natural. So there is a new nature in those who have the Spirit of God to stir them up to duty, though God’s motives of sweet encouragement and rewards may help. But the principal is to do things naturally, not out of fear or to appease other people.
"Consider, then, the necessity of a change in the inward man, of the powers of the soul. . . . And the change is especially in the will, which some would say is not touched. They would say the will is free and would give grace no more credit than necessary. But grace works upon the will most of all. For the bent and desires of the will carry the whole man with it. If the choice, and bent, and bias are the right way, by the Spirit, it is good. If the will is not inclined and formed to go the best way, there is no work of grace at all. Though all grace first comes in through the understanding being enlightened, it then goes into the will. That is, it passes through the understanding into the will, and it puts a new taste and relish upon the will and affections. You see, then, that the grace in the gospel is not mere persuasion and entreaty, but a powerful work of the Spirit entering into the soul and changing it, and altering the inclination of the will heavenward."
--Glorious Freedom (Edinburgh: Banner of Truth Trust, 2000), 55-56, 105-106.