Matthew 24:14 - Ellicott's Commentary On The Whole Bible

Shall be preached in all the world. — The words must not be strained beyond the meaning which they would have for those who heard them, and they were certain to see in “all the world” (literally, the inhabited earth, as in Luke 2:1; Acts 11:28) neither more nor less than the Roman empire; and it was true, as a matter of fact, that there was hardly a province of the empire in which the faith of Christ had not been preached before the destruction of Jerusalem. Special attention should be given to the words, “a witness unto all the nations,” i.e., to all the Gentiles, as an implicit sanction of the work of which St. Paul was afterwards the great representative. So taken, the words prepare the way for the great mission of Matthew 28:19.