Jamieson, Fausset and Brown on Mark 13:10

10. And the gospel must first be published among all nations--"for a witness, and then shall the end come" (Mt 24:14). God never sends judgment without previous warning; and there can be no doubt that the Jews, already dispersed over most known countries, had nearly all heard the Gospel "as a witness," before the end of the Jewish state. The same principle was repeated and will repeat itself to "the end."