set default-read-command

SET DEFAULT-READ-COMMAND [command]  -  define an automatic Read> command
Usually:                 next

The DEFAULT-READ-COMMAND defines a command to be executed automatically 
  when you press RETURN at the Read> prompt.  It can be set to nothing,
  so that no command is executed.  The usual setting is NEXT, which 
  shows you the next message, if any, and otherwise quits Read Mode.

To unset, type SET DEFAULT-READ-COMMAND with nothing following.

For more help, type "help" and one of the following:
(at any prompt:)  save-init   set   show
(at the Read> prompt:)   next   ?