Great Commission, n. A commandment of Christ taken to be central by
believers who live and die in fulfillment of his words in Matthew
23:15:

All authority in Heaven and on Earth has been given unto me. Go
therefore, and make converts of all nations, baptizing them in the
name of the Father, and of the Son, and of the Holy Spirit. And I
will be with you always, to the end of the age.

-The Up-to-date International Version

-- Hayward's Unabridged Dictionary