Albert Barnes Commentary 2 Samuel 7:12

"When thy days are fulfilled, and thou shalt sleep with thy fathers, I will set up thy seed after thee, that shall proceed out of thy bowels, and I will establish his kingdom." — 2 Samuel 7:12 (ASV)

The prophet, after detailing God’s past mercies to David, now moves on to a direct prophecy—one of the most important in the Old Testament.

I will set up the seed - In one sense, this manifestly refers to Solomon, David’s successor and the builder of the temple. But we have the direct authority of Peter in Acts 2:30 for applying it to Christ, the seed of David, and His eternal kingdom. The title “Son of David,” given to the Messiah in rabbinical writings and applied specifically to Jesus in the New Testament, springs mainly from the acknowledged Messianic significance of this prophecy (Acts 13:34).