John Gill Commentary 1 Kings 8:20

"And Jehovah hath established his word that he spake; for I am risen up in the room of David my father, and sit on the throne of Israel, as Jehovah promised, and have built the house for the name of Jehovah, the God of Israel." — 1 Kings 8:20 (ASV)

And the Lord has performed his word that he spoke
To David, concerning his son's building the temple:

and I am risen up in the room of David my father, and sit on the throne
of Israel, as the Lord promised ;
succeeded him in the kingdom:

and have built an house for the name of the Lord God of Israel ;
the temple he had now finished; and thus the promise to David was punctually fulfilled, that he should have a son that should succeed him in the throne, and build the house of the Lord.