Luke 11:29-30
And when the crowds thronged around Jesus, He began saying, "This generation of people is evil, [for] it is looking for a [supernatural] sign. But no [such] sign will be given to it except the sign [demonstrated in the life] of Jonah.
Luke 21:13
It will result in [an opportunity for] witnessing to them.
John 13:19
I am telling you this now, [even] before it happens, so that when it does happen, you will believe that I am [the Messiah].
John 14:29
Now I have told you this, even before it happens, so that when it does happen you will believe [in me].
John 16:4
But I have told you these things so that, when the time comes [for people to do such things], you will remember that I had warned you. I did not tell you them at the beginning [of my ministry] because I was with you [i.e., to protect you from persecution].