A man of God came from Judah to Bethel by a revelation from the Lord while Jeroboam was standing beside the altar to burn incense.
References for 1 Kings 13:1
The man of God cried out against the altar by a revelation from the Lord: "Altar, altar, this is what the Lord says, 'A son will be born to the house of David, named Josiah, and he will sacrifice on you the priests of the high places who are burning incense on you. Human bones will be burned on you.' "
References for 1 Kings 13:2
He gave a sign that day. He said, "This is the sign that the Lord has spoken: 'The altar will now be ripped apart, and the ashes that are on it will be spilled out.' "
When the king heard the word that the man of God had cried out against the altar at Bethel, Jeroboam stretched out his hand from the altar and said, "Arrest him!" But the hand he stretched out against him withered, and he could not pull it back to himself.
The altar was ripped apart, and the ashes spilled off the altar, according to the sign that the man of God had given by the word of the Lord.
Then the king responded to the man of God, "Please plead for the favor of the Lord your God and pray for me so that my hand may be restored to me." So the man of God pleaded for the favor of the Lord, and the king's hand was restored to him and became as it had been at first.