When Rehoboam arrived in Jerusalem, he mustered the whole house of Judah and the tribe of Benjamin--a hundred and eighty thousand fighting men--to make war1 against the house of Israel and to regain the kingdom for Rehoboam son of Solomon.
References for 1 Kings 12:21
But this word of God came to Shemaiah2 the man of God:3
References for 1 Kings 12:22
"Say to Rehoboam son of Solomon king of Judah, to the whole house of Judah and Benjamin, and to the rest of the people,
'This is what the LORD says: Do not go up to fight against your brothers, the Israelites. Go home, every one of you, for this is my doing.' " So they obeyed the word of the LORD and went home again, as the LORD had ordered.