'Happen' in the Bible

So Jesus replied to him, "Let it happen now, for it is right for us to fulfill all righteousness." Then John yielded to him.

So Peter took him aside and began to rebuke him: "God forbid, Lord! This must not happen to you!"

Jesus answered them, "I tell you the truth, if you have faith and do not doubt, not only will you do what was done to the fig tree, but even if you say to this mountain, 'Be lifted up and thrown into the sea,' it will happen.

As he was sitting on the Mount of Olives, his disciples came to him privately and said, "Tell us, when will these things happen? And what will be the sign of your coming and of the end of the age?"

You will hear of wars and rumors of wars. Make sure that you are not alarmed, for this must happen, but the end is still to come.

For then there will be great suffering unlike anything that has happened from the beginning of the world until now, or ever will happen.

How then would the scriptures that say it must happen this way be fulfilled?"