Charles Ellicott Commentary 2 Kings 20:8

"And Hezekiah said unto Isaiah, What shall be the sign that Jehovah will heal me, and that I shall go up unto the house of Jehovah the third day?" — 2 Kings 20:8 (ASV)

What shall be the sign ...? —Compare 2 Kings 19:29 and note; Isaiah 7:11 and following, where Isaiah requests Ahaz to choose a sign. The sign was obviously a token that the prophet’s word would come true.