““My father David had it in his heart to build a temple for the Name of the Lord, the God of Israel. But the Lord said to my father David, ‘You did well to have it in your heart to build a temple for my Name. Nevertheless, you are not the one to build the temple, but your son, your own flesh and blood—he is the one who will build the temple for my Name.’ “The Lord has kept the promise he made: I have succeeded David my father and now I sit on the throne of Israel, just as the Lord promised, and I have built the temple for the Name of the Lord, the God of Israel.” – 1 Kings 8:17-20 NIV

God had promised Solomon’s father, David, a temple to be built by his ancestors after he had died. We can see by Solomon finishing the temple that God had fulfilled his promise to David. Solomon then goes on to speak about the second promise God gave to David.

““Now Lord, the God of Israel, keep for your servant David my father the promises you made to him when you said, ‘You shall never fail to have a successor to sit before me on the throne of Israel, if only your descendants are careful in all they do to walk before me faithfully as you have done.’” – 1 Kings 8:25 NIV

Solomon basically says please continue to keep the other promise you made to my father to always have a descendant of David on the throne as long as Israel is faithful. I’m not sure where Solomon’s heart was at here, but I know God has been faithful and demonstrated it many many times before. There should be no reason for concern for Solomon that God won’t keep his promises, and we shouldn’t be concerned about God keeping his promises either.