God told Solomon that his kingdom would be divided after his death because he turned away from God and worshipped other gods, influenced by his many foreign wives. This is recorded in 1 Kings 11:1-13, where Solomon's idolatry angered God, leading to the prophecy that the kingdom would be torn away from his son, Rehoboam, and divided. However, for the sake of David, his father, God allowed Solomon to rule until his death before the division occurred.