'Happen' in the Bible

This is the revelation of Jesus the Messiah, which God gave him to show his servants the things that must happen soon. He made it known by sending his messenger to his servant John,

Therefore, write down what you have seen, what is, and what is going to happen after this.

After these things, I saw a door standing open in heaven. The first voice that I had heard speaking to me like a trumpet said, "Come up here, and I will show you what must happen after this."

He told me, "These words are trustworthy and true. The Lord God of the spirits and of the prophets has sent his messenger to show his servants the things that must happen soon."