God promises destruction of Jerusalem, the capital city of the Jewish nation of Israel, in the Gospel of Jesus Christ. This is Gospel Truth, literally.
God promises destruction of Jerusalem in the Gospel of Luke, chapter 21. This is the promise of God. God keeps His promises. And that is why Jerusalem was destroyed in 70 AD. God kept His promise to destroy Jerusalem, using Gentile armies.
But just like prophecies in the Book of Daniel and in the Book of Isaiah keep becoming fulfilled again and again, so will the prophecy in the Gospel of Luke, chapter 21. See Revelations 11.
Jerusalem will be destroyed before the Second Coming of Jesus Christ, as prophecied in the Holy Bible. God will keep His promise made in the Book of Revelations to destroy Jerusalem (the capital city of the Jewish nation of Israel) before the Second Coming of Jesus Christ. It is the Word of God for the People of God.