John Gill Commentary 1 Kings 20:22

"And the prophet came near to the king of Israel, and said unto him, Go, strengthen thyself, and mark, and see what thou doest; for at the return of the year the king of Syria will come up against thee." — 1 Kings 20:22 (ASV)

And the prophet came to the king of Israel
The same that came to him before:

and said unto him, go, strengthen yourself ;
exhorted him to fortify his cities, especially Samaria, and increase his army, that he might be able to oppose the king of Syria:

and mark, and see what you do :
observe his moral and religious actions, and take heed that he did not offend the Lord by them, as well as make military preparations:

for at the return of the year the king of Syria will come up against
you ;
about the same time in the next year, at the spring of the year, when kings go out to war, see (2 Samuel 11:1) .