Hezekiah recovered as the Lord said he would. It is rather surprising, however, after the astonishing nature of the sign, to be told that recovery itself was accomplished by something as mundane as the preparation and application of a poultice! But if we are surprised, it is because of a defect in our own theology rather than anything incongruous in the text. For there is no disjunction in Scripture between miraculous and natural healing, as though God were involved in one and not the other. He is as much Lord of the soothing poultice as he is of the moving shadow, and perhaps our eyes would be more open and our hearts more thankful if only we could grasp this simple and sane biblical truth more firmly.
Barry Webb, The Message of Isaiah (comments on Isaiah 38