Behold, I will send my messenger, and he shall prepare the way before me: and the Lord, whom ye seek, shall suddenly come to his temple, even the messenger of the covenant, whom ye delight in: behold, he shall come, saith the LORD of hosts.
But who may abide the day of his coming? and who shall stand when he appeareth? for he [is] like a refiner’s fire, and like fullers’ soap:
And he shall sit [as] a refiner and purifier of silver: and he shall purify the sons of Levi, and purge them as gold and silver, that they may offer unto the LORD an offering in righteousness. — Mal 3:1-3
According to the Hebrew calendar on the first day of seventh month (the month of Nisan) of every year God’s people celebrate the Feast of Trumpets, a holy day and a high Sabbath Lev 23:24.