'Happen' in the Bible

Peter took Him aside and began to rebuke Him, saying, “God forbid it, Lord! This shall never happen to You.”

And Jesus answered and said to them, “Truly I say to you, if you have faith and do not doubt, you will not only do what was done to the fig tree, but even if you say to this mountain, ‘Be taken up and cast into the sea,’ it will happen.

How then will the Scriptures be fulfilled, which say that it must happen this way?”