Charles Spurgeon Commentary 2 Samuel 7:3

"And Nathan said to the king, Go, do all that is in thy heart; for Jehovah is with thee." — 2 Samuel 7:3 (ASV)

He spoke too fast. Even prophets, who are inspired by God, must wait on their Master for their message; and when they utter words that come only from their own mouths, they say what they will have to unsay before long. It did look very clear that this was the proper thing for Nathan to say to David; but he did not have a "Thus saith the Lord" for it.