I can say out loud that grace is free and I still catch myself keeping score with God. Why can I not stop trying to earn it?

“Ho, every one that thirsteth, come ye to the waters, and he that hath no money; come ye, buy, and eat; yea, come, buy wine and milk without money and without price. Wherefore do ye spend money for that which is not bread? and your labour for that which satisfieth not? hearken diligently unto me, and eat ye that which is good, and let your soul delight itself in fatness.”

Isaiah calls out to exiles in the voice of a market trader, offering food and drink to people who have no money. The strangeness is the point, because everything else in an ancient marketplace had a price and this does not. He then asks why they keep spending on what never satisfies them. Working to buy what is being handed out free is a very old human habit, not a modern neurosis.

“Are ye so foolish? having begun in the Spirit, are ye now made perfect by the flesh?”

Paul is writing to churches he planted who were being told that faith in Christ needed topping up with careful law keeping. His question is almost exasperated: you began by receiving, so why switch to earning now? These were not lazy believers. They were sincere ones drifting toward performance, and sincerity is exactly the temperament that finds free grace hardest to accept.