What did you say???

When your days are fulfilled and you lie down with your fathers, I will raise up your offspring after you, who shall come from your body, and I will establish his kingdom. He shall build a house for my name, and I will establish the throne of his kingdom forever. I will be to him a father, and he shall be to me a son. When he commits iniquity, I will discipline him with the rod of men, with the stripes of the sons of men, but my steadfast love will not depart from him, as I took it from Saul, whom I put away from before you. And your house and your kingdom shall be made sure forever before me. Your throne shall be established forever.’” In accordance with all these words, and in accordance with all this vision, Nathan spoke to David.
Then King David went in and sat before the LORD and said, “Who am I, O Lord GOD, and what is my house, that you have brought me thus far? And yet this was a small thing in your eyes, O Lord GOD. You have spoken also of your servant's house for a great while to come, and this is instruction for mankind, O Lord GOD! (2 Samuel 7:12-19 ESV)
Forever is a long time.  Kings come and kings go.  David had seen that in his own life.  As Nathan here shares with Him God's words, he is taken back, made speechless, totally humbled.  What kind of promise was this?  He had plenty of sons to choose from - too many, in fact.  But this promise was beyond that.  Sometimes it seemed to David that the promises of God went beyond the immediate, or even the near future, like his son being the one to build the temple.  It was if God was looking much further into the distance toward eternity, to a time when One of his offspring would have a kingdom that was bigger than any one could imagine. David could sense that, he says.  And yet this was a small thing in your eyes, O Lord GOD. You have spoken also of your servant's house for a great while to come, and this is instruction for mankind, O Lord GOD! (v. 19) This promise was bigger than David or Israel or any nation. It was for all mankind.  What a King!  What a promise.