“And the L-RD spake unto Moses, saying, 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” (Leviticus 23:23-24).
There is mystery surrounding what is commonly called Rosh Hashanah (The Feast of Trumpets). Unlike the other six Messianic feasts, it has no name in Scripture. It is simply referred to as Yom Teruah (תְּרוּעָה: Day of alarm, or shouting, or trumpet blast). It is a memorial, but what is being memorialized is uncertain. Jewish liturgy describes it as Yom HaDin (Day of Judgment). Although it is to be on the first day of Tishri, the seventh month of the Hebrew year, ascertaining the day is dependent on atmospheric conditions that sometimes obscure the delicate crescent of the new moon. It could be said: “of that day and hour knoweth no man.”
Paul writes of another trumpet blast in 1 Corinthians 15:51-52: “Behold, I show you a mystery; We shall not all sleep, but we shall all be changed, in a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.”
And again in 1 Thessalonians 4:16-17: “For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.”