Joel 2:1-2

Let the horn be sounded in Zion, and a war-cry in my holy mountain; let all the people of the land be troubled: for the day of the Lord is coming; For a day of dark and deep shade is near, a day of cloud and black night: like a black cloud a great and strong people is covering the mountains; there has never been any like them and will not be after them again, from generation to generation.