See where I am sending an angel of mine, to make the way ready for my coming! All at once the Lord will visit his temple; that Lord, so longed for, welcome herald of a divine covenant. Ay, says the Lord of hosts, he is coming; but who can bear the thought of that advent? Who will stand with head erect at his appearing? He will put men to a test fierce as the crucible, searching as the lye that fullers use. From his judgement-seat, he will refine that silver of his and cleanse it from dross; like silver or gold, the sons of Levi must be refined in the crucible, ere they can offer the Lord sacrifice duly performed. Then once more the Lord will accept the offerings of Juda and Jerusalem, as he did long since, in the forgotten years. Come I to hold assize, not slow to arraign the sorcerer, the adulterer, the forsworn, all of you that deny hired man his wages, widow and orphan redress, the alien his right, fearing no vengeance from the Lord of hosts. In me, the Eternal, there is no change, and you, sons of Jacob, are a people still.
Yours to keep the law ever in mind, statute and award I gave to assembled Israel through Moses, that was my servant. And before ever that day comes, great day and terrible, I will send Elias to be your prophet; he it is shall reconcile heart of father to son, heart of son to father; else the whole of earth should be forfeit to my vengeance.
Malachias iii. 1-6, iv. 4-6.