Malachi 3:2

3:2 Who can endure the day of his coming? Who can keep standing when he appears? For he will be like a refiner’s fire, ¹  like a launderer’s soap.

Malachi 4:5

4:5 Look, I will send you Elijah ²  the prophet before the great and terrible day of the Lord arrives.

[3:2]  ¹ sn The refiner’s fire was used to purify metal and refine it by melting it and allowing the dross, which floated to the top, to be scooped off.

[4:5]  ² sn I will send you Elijah the prophet. In light of the ascension of Elijah to heaven without dying (2 Kgs 2:11), Judaism has always awaited his return as an aspect of the messianic age (see, e.g., John 1:19-28). Jesus identified John the Baptist as Elijah, because he came in the “spirit and power” of his prototype Elijah (Matt 11:14; 17:1-13; Mark 9:2-13; Luke 9:28-36).