Exposition of the entire bible by Gill

And this Gospel of the kingdom,.... Which Christ himself
preached, and which he called and sent his apostles to
preach, in all the cities of Judah; by which means men
were brought into the kingdom of the Messiah, or Gospel
dispensation; and which treated both of the kingdom of
grace and glory, and pointed out the saints' meetness for
the kingdom of heaven, and their right unto it, and gives
the best account of the glories of it:
shall be preached in all the world; not only in Judea,
where it was now confined, and that by the express
orders of Christ himself; but in all the nations of the
world, for which the apostles had their commission
enlarged, after our Lord's resurrection; when they were
bid to go into all the world, and preach the Gospel to
every creature; and when the Jews put away the Gospel
from them, they accordingly turned to the Gentiles; and
before the destruction of Jerusalem, it was preached to
all the nations under the heavens; and churches were
planted in most places, through the ministry of it:
for a witness unto all nations; meaning either for a
witness against all such in them, as should reject it; or as
a testimony of Christ and salvation, unto all such as
should believe in him:
and then shall the end come; not the end of the world, as
the Ethiopic version reads it, and others understand it;
but the end of the Jewish state, the end of the city and
temple: so that the universal preaching of the Gospel all
over the world, was the last criterion and sign, of the
destruction of Jerusalem; and the account of that itself
next follows, with the dismal circumstances which
attended it.