Albert Barnes Commentary Isaiah 38:4

"Then came the word of Jehovah to Isaiah, saying," — Isaiah 38:4 (ASV)

Then came the word of the Lord - In the parallel place in 2 Kings 20:4, it is said, And it came to pass, before Isaiah was gone out into the middle court, that the word of the Lord came to him. That is, the message of God came to Isaiah before he had left Hezekiah; or as soon as he had offered his prayer. This circumstance is omitted by Isaiah on the revision of his narrative which we have before us. But there is no contradiction. In this place it is implied that the message came to him soon, or immediately.