A.T. Robertson Commentary Mark 13:10

"And the gospel must first be preached unto all the nations." — Mark 13:10 (ASV)

Must first be preached (πρωτον δε κηρυχθηνα). This only in Mark. It is interesting to note that Paul in Col 1:6,23 claims that the gospel has spread all over the world. All this was before the destruction of Jerusalem.