Isaiah 38:8

8.Lo, I bring back the shadow of degrees. The sign which is here given to Hezekiah is the going back of the shadow on the sundial, along with the sun, ten degrees by which it had already gone up, (78) that is, had advanced above the horizon. And this sign bears a resemblance to the event itself, as all other signs generally do; for it is as if he had said, “As it is in my power to change the hours of the day, and to make the sun go backwards, so it is in my power to lengthen thy life.” As to the shadow not going back as many degrees as there were years added to his life, that was impossible, because there were not more than twelve degrees on the sundial; for the day was divided by them into twelve hours, either longer or shorter, according to the change of the season. We need not, therefore, give ourselves any uneasiness about the number; it is enough that there is a manifest correspondence and resemblance.

On the sundial of Ahaz. (79) Here the Jews make fables according to their custom, and contrive a story, that the day on which Ahaz died was shorter than ten hours, and that what God had justly inflicted on him as a punishment for his sins was reversed for the benefit of Hezekiah; because the shortening of one day was the lengthening of another. But there is no history of this, and it is entirely destitute not only of evidence but of probability; nor is there anything said here about the death of Ahaz, or about the change which took place when he died, but about the sundial which he had made.