John Gill

And Nathan departed unto his house,.... His own house, which probably was in the city of Jerusalem, having delivered his message, and brought David to a sense of his sin, and declared to him from the Lord the forgiveness of it; yet for the honour of religion, and the stopping of the mouths of blasphemers, the death of the child is threatened and foretold, and then Nathan took his leave of him, having nothing more from the Lord to say to him: and the Lord struck the child that Uriah's wife bare unto David; for so she was, and not David's wife, when this child was begotten of her; and, as a mark of God's displeasure at the sin of adultery, the child was struck with a sore disease by the immediate hand of God: and it was very sick; even unto death, as the event showed.