John Gill Commentary 2 Samuel 7:16

"And thy house and thy kingdom shall be made sure for ever before thee: thy throne shall be established for ever." — 2 Samuel 7:16 (ASV)

And your house and your kingdom shall be established for ever
before you
That is, both his family and his government should be perpetuated, or he should always have one of his family to sit upon his throne; the accomplishment of which, in the beginning of it, he saw with his eyes in his son Solomon, and with an eye of faith in his greater Son the Messiah, in whom only these words will have their complete fulfilment.

And so Abarbinel says this vision or prophecy is explained by some of the days of the Messiah; and this house and kingdom, in (1 Chronicles 17:14) ; are called by the Lord "my" house, and "my" kingdom:

your throne shall be established for ever ;
which is a repetition of the same in other words for the confirmation of it.