The Prophecy of Yom Teruah/(The Day of Shouting) The Feast of Trumpets

What is Yom Teruah and why should we observe this day?

"Speak unto the children of Israel, saying, In the seventh month, in the first day of the month, shall ye have a sabbath, a memorial of blowing of trumpets, an holy convocation." (Leviticus 23:24) 

"After this I kept looking in the night visions, and behold, a fourth beast, dreadful and terrifying and extremely strong; and it had large iron teeth. It devoured and crushed and trampled down the remainder with its feet; and it was different from all the beasts that were before it, and it had ten horns. 

"While I was contemplating the horns, behold, another horn, a little one, came up among them, and three of the first horns were pulled out by the roots before it; and behold, this horn possessed eyes like the eyes of a man and a mouth uttering great boasts. "I kept looking Until thrones were set up, And the Ancient of Days took His seat; His vesture was like white snow And the hair of His head like pure wool. His throne was ablaze with flames, Its wheels were a burning fire. "A river of fire was flowing And coming out from before Him; Thousands upon thousands were attending Him, And myriads upon myriads were standing before Him; The court sat, And the books were opened." (Daniel 7:7-10) 

"Blow ye the trumpet in Zion, and sound an alarm in my holy mountain: let all the inhabitants of the land tremble: for the day of the LORD cometh, for it is nigh at hand; A day of darkness and of gloominess, a day of clouds and of thick darkness, as the morning spread upon the mountains: a great people and a strong; there hath not been ever the like, neither shall be any more after it, even to the years of many generations." (Joel 2:1-2)