Luke 21:13

“It will turn out to you for a testimony.”

But none of these things should disturb them, for it will result in their being able to testify before men concerning Him. It will be a part of their overall testimony. It will also result in the end in their being testified to by Him before the Father (Luke 12:8). Note that Luke here omits Mark 13:10 (the Good News will be preached to all nations, compare Romans 1:5) because he is concerned to keep the emphasis on their suffering for Christ's sake, but the idea behind the words is necessarily assumed in order for the persecutions to take place. ‘All nations' in those early days would be seen as signifying all known nations. And later Luke is at pains to point out that even at Pentecost itself there were people from ‘every nation under heaven' (Acts 2:5). We can compare also Romans 1:8, where Paul is able to say ‘your faith is proclaimed in all the world'. Their ‘world' was not as large as ours.