Healing the royal official's son is one of the miracles of Jesus that appears in the Gospel of John (John 4:46-54). This episode takes place at Cana, though the official's son is some distance away, at Capernaum.
In the Gospel of John (NIV):
A similar episode appears in the Gospels of Matthew 8:5-13 and Luke 7:1-10, as Healing the Centurion's servant. While Fred Craddock treats these as the same miracle, R. T. France considers them separate miracles.