Chapter 13
A man of God, unnamed, goes to Bethel and prophesies that by God's own hand that this altar will be torn down, and these false priests will be sacrificed there - human bones will be on the altar. He says that a son of David named Josiah will one day burn the false priests on this altar. As a sign that what he says is true, the man of God says this very altar will be overturned and the ashes will spill out on the ground. J points at the man with his hand/finger, and orders the man seized. But God "dries up" the hand doing the pointing, so that J cannot pull it back in. Then God tears down the altar, just as the man of God said.
2021 - We will see later, during Josiah's reign, that these false prophets are indeed sacrificed on this altar...which they apparently rebuild after the incident. It seems certain that this verse, vs 2 which names Josiah, is used to "prove" this wasn't written until after Josiah's reign, and that this prophecy was inserted after the fact. Not sure when the Book Notes in MSB say it was written, but it would have been well before Josiah's reign. Hundreds of years before in fact.
J asks the man of God to pray, and ask that his hand be restored. The man of God does so, and the hand is restored. Because of this restoration, J asks this man of God to come home with him, but the man refuses, because God has told him not to eat or drink in that place. He leaves. Then an "old prophet" in Bethel (presumably this is the Bethel in Benjamin that sided with the northern kingdom. It would be wise to be skeptical of such a prophet) hears of it, catches up with him, and tells the man of God that an angel told him to get the man of God to come home with him to Bethel and eat with him. But this old prophet is lying. Still, the man of God goes with him. What is the principle here? How would the man of God have known? Maybe because God's instructions covered the whole time period - including the injunction to go home a different way than he had come up - from door to door. God's instructions did not stop at the point where the ashes were spilled. God's instructions should have been followed all the way to the end, but the man of God was persuaded to turn aside before he had completed God's commands. Maybe. Seems like this could be it. Additional factors from MSB: God had told the man of God to go home a different way so that he would not be recognized. The whole reason for the man not receiving hospitality - from ANYONE - on this trip was so that God's complete rejection of the northern tribes would be made clear. As the man of God had nothing to do with Israel, God would have nothing further to do with Israel. God was declaring the 10 tribes apostate in their entirety. At this point, it was over for Israel. It will be many years before the Assyrians put the last nail in the coffin, but they are already in the coffin. MSB says the man of God, upon hearing about an angelic change of orders, should himself have sought divine guidance in the matter, should have confirmed first hand that God's command had changed. Instead, he took the "old prophet" at his word.
God tells the man of God that because he's been taken in, and not done what God himself told him to do, he will not get home to be buried in the tomb of his fathers. On his way home a lion kills him. The old prophet goes and gets the body and buries it in his own grave, and orders his sons to bury him with the man of God when he dies.
So Jeroboam is unphased by all this, and appoints more priests and builds more high places. We find the result here:
34 And this thing became sin to the house of Jeroboam, so as to cut it off and to destroy it from the face of the earth. [1Ki 13:34 ESV]
So this early in Israel's history as a separate nation from Judah, Jeroboam's sin has sealed it's fate. It will be gone, and never be seen again. It is several hundred years before this happens, but it does come about.