John Gill Commentary 1 Kings 9:5

"then I will establish the throne of thy kingdom over Israel for ever, according as I promised to David thy father, saying, There shall not fail thee a man upon the throne of Israel." — 1 Kings 9:5 (ASV)

Then I will establish the throne of your kingdom upon Israel for
ever
In a succession in his posterity, until the coming of the Messiah:

as I promised unto David your father, saying, there shall not fail you
a man upon the throne of Israel ;
not fail one of his posterity to sit upon it; see (2 Samuel 7:12 2 Samuel 7:13) (Psalms 132:11Psalms 132:12) .