This particular gospel message Jesus is speaking about is the concerning the End of the Age, a message (gospel) about the "KINGDOM", the message that concerns the very End of all things as we know it now with man.
Matthew 24:14 And when this gospel (message) of the "KINGDOM" will be preached into all the world as a testimony to all nations, then the End will come.
Many pious teachers assumed Matthew 24:14 to be a command for them to go into all the world and preach the gospel message of accepting Jesus and repentance...but this is not what our Lord Jesus is referring to. The command to go into the world making disciples is given in Matthew 28:19 and not Matthew 24:14.
Our Lord has not give this command to any man to fulfill as Jesus spoke about this to his disciples, as this gospel message will be spoken by an angel at the very End at Jesus coming and then the End will come. Yes, our Lord has recorded this event taking place in the End in the book of Revelations.
Rev 14:6 is the verse telling us "WHO" fulfills Jesus' words in Matt 24:14
Rev 14:6 Then I saw another "ANGEL" flying in mid-air "AND HE HAD THE ETERNAL GOSPEL TO PROCLAIM" to those who live upon the earth----to every nation, tribe, language and people.
In the next verse this 'ANGEL' is fulfilling Matthew 24:14 as the gospel message is given into all the world and that is for all mankind to now worship the Lord and to Fear the Lord and give him glory. amen.
Rev 14:7 He, the "ANGEL" said in a loud voice, "fear God and give HIM GLORY because the HOUR of HIS JUDGMENT HAS COME.
Rev 14 is the chapter that speaks of the End taking place, the Lord standing upon the mount of Olives and it is during these last moments of men's government existing that a session of angels are appearing each having a part in these EVENTS of the very End as recorded for us to understand and be prepared in as we are God's children who he has written these things for us to understand.
In Christ's precious truths
Vickie