set reply-insert

SET REPLY-INSERT NO/yes  -  whether to include the original in the reply

With the usual NO setting, when you REPLY to a message, that message is
  not included in your reply.  You can use the option "including" to
  include the original message.

If you change it to YES, the original is always included, and you have to
  use the option "not including" when you do not want it included.

For more help, type "help" and one of the following:
(at any prompt:)  save-init   set   show   set reply-indent
(at the MM> or Read> prompts:)  reply