See, I am sending my messenger to prepare the way before me, and the Lord whom you seek will suddenly come to his temple. The messenger of the covenant in whom you delight—indeed, he is coming, says the Lord of hosts.
But who can endure the day of his coming, and who can stand when he appears? For he is like a refiner's fire and like fullers' soap;
he will sit as a refiner and purifier of silver, and he will purify the descendants of Levi and refine them like gold and silver, until they present offerings to the Lord in righteousness.
References for Malachi 3:3
Then the offering of Judah and Jerusalem will be pleasing to the Lord as in the days of old and as in former years.
Then I will draw near to you for judgment; I will be swift to bear witness against the sorcerers, against the adulterers, against those who swear falsely, against those who oppress the hired workers in their wages, the widow and the orphan, against those who thrust aside the alien, and do not fear me, says the Lord of hosts.
For I the Lord do not change; therefore you, O children of Jacob, have not perished.