Shemaiah the Prophet lived in the time of Rehoboam, Solomon’s son. Just after the schism between the northern kingdom of Israel, led by Jeroboam, and the southern kingdom of Judah, led by Rehoboam, Rehoboam gathered an army of 180,000 men to re-unite the kingdom. God sent Shemaiah to warn him that the schism was from God, that the Israelites were family, and that war would end badly for him (2 Chronicles 11:1–4). He returns home.
Later, after Egypt swept across Judah, God sent Shemaiah again to explain what happened: “You abandoned me [God], so I have abandoned you to the hand of Shishak [King of Egypt]” (2 Chronicles 12:5). Rehoboam and the leaders repent, and Shemaiah announces that as a result, Jerusalem would be conquered, but not destroyed. And so it is. Like Iddo, Shemaiah wrote the story of Rehoboam in a lost book called The Record of Shemaiah the Prophet (2 Chronicles 12:15).