1Look, I am sending my messenger who will clear the path before me;
suddenly the Lord whom you are seeking will come to his temple.
The messenger of the covenant in whom you take delight is coming,
says the Lord of heavenly forces.
2 Who can endure the day of his coming?
Who can withstand his appearance?
He is like the refiner’s fire or the cleaner’s soap.
3 He will sit as a refiner and a purifier of silver.
He will purify the Levites
and refine them like gold and silver.
They will belong to the Lord,
presenting a righteous offering.
4 The offering of Judah and Jerusalem will be pleasing to the Lord
as in ancient days and in former years
-Malachi 3:1-4 CEB
It's a well known trope within movies, TV, and books. The mirror knows all. Frank L. Baum incorporated it twice. Once with the Gnome King's mirror, that can see where ever he asks for it to see. The second time with Zixi the Queen of Ixi. This queen, who was over 600 years old, used magic to make herself look 16. Her mirror, conversely showed her real age.
The one that immediately came to my mind was The Mirror Gate from The Neverending Story. It was one of the tests in order to get to the Southern Oracle. When the traveler came to the gate, they had to look in the mirror to pass. The reflection would show the honest view of the person:
Engywook: Next is the Magic Mirror Gate. Atreyu has to face his true self.
Falcor: So what? That won't be too hard for him.
Engywook: Oh, that's what everyone thinks! But kind people find out that they are cruel. Brave men discover that they are really cowards! Confronted by their true selves, most men run away screaming!
Atreyu discovered Bastian because Atreyu was only an avatar for Bastian's adventure. (Atreyu doesn't realize that when he sees it, and simply passes through.)
When I read Malachi 3:2-3 I imagine God much like one of those magic mirrors. The reason we wouldn't be able to endure the day of his coming, is because we would be left with only the truth of who and what we were. It's that "refiners fire and cleaner's soap" referred to in scripture. That would be enough to make "kind people find out that they are cruel. Brave men discover that they are really cowards!" Basically, enough to help us all see we are fallen creatures, all of us. None of us are perfect. All of us fall short of the glory of God.
Just something to think about. On a side note, there are times I feel like I've been put before God, and I have felt that boiled down truth. It helps me find humility towards others, even if sometimes I'm not humble. It helps me find kindness, even if sometimes I'm not kind. God's truth always makes us better, even if seeing the truth isn't something we are drawn to do.