Compare 2 Kings 20 and notes. The “sign” is not (as in the margin) the miraculous cure, but the going back of the shadow on the dial of Ahaz (see 2 Chronicles 32:31).
Related Commentaries of 2 Chronicles 32:24
2 Chronicles 32:24
24 In those days Hezekiah was sick to the death, and prayed unto the LORD: and he spake unto him, and he gavei him a sign.