Albert Barnes Commentary 1 Kings 11:36

"And unto his son will I give one tribe, that David my servant may have a lamp alway before me in Jerusalem, the city which I have chosen me to put my name there." — 1 Kings 11:36 (ASV)

That David may have a light - See the references in the margin. The exact meaning of this expression is uncertain. Perhaps the best explanation is that “light” here is understood as the essential feature of a continuing “home.”