1.14 Synoptics -- Persecution
Mat 10:16-23, Mk 13:9-13, Lk 21:10-19. Jesus taught the disciples about bearing witness under persecution.
"On my account you will be brought before governors and kings as witnesses to them and to the Gentiles" (Mat 10:18).
Matthew inserts these words in the context of sending the disciples out on their training mission, but Jesus clearly referred to a later time, since no persecution occurred till after Jesus' death. So for Matthew, the "trial run" was to go only to Israel, but later the disciples would be be sent farther afield. Mark and Luke change the setting of this teaching. They insert it as part of Jesus' prophecy about the end of the age: in the midst of the fall of Jerusalem, false Messiahs, wars and rumors of wars.
"And the gospel must first be preached to all nations" (Mk 13:10).
This makes sense. Luke does not specifically mention the Gentiles, just the part about giving witness before kings and governors. Still, this leaves Matthew and Mark both explicitly including Gentiles in the near future.