"I will rejoice in doing them good."
But this assurance was originally given to a group of people described by God as those who "have done nothing but evil in my sight from their youth" (verse 30, NIV). They were in captivity in Babylon because of their sins over many generations.
Just a few chapters earlier, God had said to them: "This is what the Lord says: 'When seventy years are completed for Babylon, I will come to you and fulfill my gracious promise to bring you back to this place. For I know the plans I have for you,' declares the Lord, 'plans to prosper you and not to harm you, plans to give you hope and a future'" (Jeremiah 29:10-11, NIV). If anyone qualified for demerits, surely the Israelites in captivity did. Yet God promised to prosper them, to rejoice in doing them good.