John Gill Commentary Isaiah 38:22

"Hezekiah also had said, What is the sign that I shall go up to the house of Jehovah?" — Isaiah 38:22 (ASV)

Hezekiah also had said Unto Isaiah, as in (2 Kings 20:8): what is the sign that I shall go up to the house of the Lord? both of his health, and of his going up to the temple with thanksgiving for it; though the former is not here mentioned, as it is elsewhere; partly because it is supposed in the latter, for without that he could not have gone up to the temple; and partly because he was more solicitous for the worship and honour of God in his house, than for his health.

The Syriac version transposes these verses, "Hezekiah had said, what is the sign? &c. and Isaiah had answered, let them take a lump of figs" as if this latter was the sign; whereas it was that of the sun's going down ten degrees on the dial of Ahaz, (Isaiah 38:7Isaiah 38:8), (See Gill on Isaiah 38:7), (See Gill on Isaiah 38:8).