1 Kings 11:13

but he will have one tribe, for the sake of My servant David and for the sake of Jerusalem, the city which I have chosen from all the tribes of Israel,

‘But to his son I will give one tribe, that My servant David may have a lamp always before Me in Jerusalem, the city where I have chosen for Myself to put My name.

But as for the sons of Israel who lived in the cities of Judah, Rehoboam reigned over them.

Now it happened when all Israel heard that Jeroboam had returned, that they sent and called him to the congregation and made him king over all Israel. None but the tribe of Judah followed the house of David.

So Yahweh was very angry with Israel and caused them to depart from His presence; none was left except the tribe of Judah alone.

‘Indeed I will defend this city to save it for My own sake and for My servant David’s sake.’”

However, Yahweh was not willing to make the house of David a ruin because of the covenant which He had cut with David, and since He had promised to give a lamp to him and his sons forever.