Howbeit I will not rend away all the kingdom; but will give one tribe to thy son for David my servant’s sake, and for Jerusalem’s sake which I have chosen. (1 Kings 11:13)
Except for David’s sake, the whole kingdom would have been taken away from Solomon’s son. As it was, only one tribe, Judah (ch. 12:20), was reserved to the house of David. Benjamin and Levi (2 Chron. 11:12, 13), were to be with Judah, and were included with Judah to make one nation.