2. Speak tenderly to Jerusalem.
So here, the heart, groaning and sighing, is comforted by the Spirit, for the Spirit speaks to the heart as He wills. Do you want a gracious God? He answers: “You have a gracious God.” Do you want to be comforted? He answers: “You are comforted.” Here, then, you observe God’s people, afflicted and sad. To them the Gospel is spoken, to their heart and feeling. For Gospel preachers are commanded to say joyful things, more than the heart can grasp, as Paul says (Rom. 8:26), “with sighs too deep for words.” So these groans are comforted with consolations too deep for words. Let the preacher say, then: “I not only preach Christ to you as the One who forgives, but I also give you His righteousness, so that, clothed with Him, you may have all that is His. The comfort is therefore far more excellent than all groanings. Do you want to be holy? I will make you holy, yes, most holy through Christ.”
Luther’s Works Vol. 17: Lectures on Isaiah Chapters 40-66