[As Solomon grew old, his wives turned his heart after other gods, and his heart was not fully devoted to the LORD his God, as the heart of David his father had been. 1 Kings 11:4 NIV ]
The LORD became angry with Solomon because his heart had turned away from the LORD, the God of Israel, who had appeared to him twice.
Although he had forbidden Solomon to follow other gods, Solomon did not keep the LORD's command. So the LORD said to Solomon, "Since this is your attitude and you have not keep my covenant and my decrees, which I commanded you, I will most certainly tear the kingdom away from you and give it to one of your subordinates. Nevertheless, for the sake of David your father, I will not do it in your lifetime. I will tear it out of the hand of your son. Yet I will not tear the whole kingdom from him, but will give him one tribe for the sake of David my servant and for the sake of Jerusalem, which I have chosen." 1 King 11:9-13 NIV