What does Simon prophesize and how is this important

Simon tells Ralph that he will get rescued. He does not know why, he just thinks so.

You'll get back to where you came from.' Simon nodded as he spoke. He was kneeling on one knee, looking down from a higher rock which he held with both hands; his other leg stretched down to Ralph's level. Ralph was puzzled and searched Simon's face for a clue. 'It's so big, I mean----" Simon nodded. 'All the same. You'll get back all right. I think so, anyway.'

This prophecy is very much in line with Simon's characterization as a Christ-figure throughout the story.