John Gill Commentary 2 Samuel 7:28

"And now, O Lord Jehovah, thou art God, and thy words are truth, and thou hast promised this good thing unto thy servant:" — 2 Samuel 7:28 (ASV)

And now, O Lord God, you [are] that God
Who is the Lord of hosts, and the God of Israel, that has promised and is able to perform, and is faithful to his promise:

and your words be true ;
are truly, punctually, and faithfully performed, never fail:

and you have promised this goodness unto your servant ;
concerning building and establishing his house. David repeats this promise as being greatly affected with it, and fully assured of the performance of it.