1 Kings 22:17
And he said, I saw all Israel scattered upon the hills, as sheep that have not a shepherd: and the LORD said, These have no master: let them return every man to his house in peace. And he said, I saw all Israel scattered upon the hills, as sheep that have not a shepherd: and the LORD said, These have no master: let them return every man to his house in peace.
Ahab counted Micaiah as an enemy because Micaiah prophesied evil against him. The verse gives Micaiah's vision of all Israel scattered upon the hills like sheep that have no shepherd, with the Lord declaring that these have no master and directing every man to return to his house in peace.
Having no shepherd and having no master means the army would be left without its king to lead it. The vision warned that the kings' planned battle, the campaign against Ramoth-gilead and against the Syrians, was not favored by heaven and would not end in victory.
It foretold the dispersal of Israel's armies and their return home after Ahab's death. This was fulfilled after Ahab died, when a proclamation went out sending each man back to his own city and to his own country. Ahab could have been saved by accepting this warning, but he rejected it and perished.