The worm will turn to lift this exposed area as far from the abrasive sand as possible, and it will take you with it to the top.
10 seconds sound clip from the Dune (1984) movie soundboard.
You can hear this line at 02:17:15 in the Blu-ray version of the movie.
Quote context
[...]
- Yet in order to lead them, I must conquer the worm, conquer Shai-Hulud.
- Usul, it is time you become a sand rider and travel as a Fremen.
- Take the kiswa maker hook of our sietch and ride as a leader of men.
- Two thumpers are planted. The worm may not surface for the first. He will rise for the second.
- As he approaches, the sand will engulf you.
- Wait till the head of the worm passes, then go quickly.
- I must not fear. Fear is the mind killer.
[...]