Charles Ellicott 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)

Go, do all that is in thine heart. —Nathan naturally considered that it must be right for David to execute his pious purpose; but he spoke only according to his own sense of right, and not by Divine direction.