2 Nephi 23

3 witnesses of Christ here.

The Day of the Lord

Howl ye, for the day of the Lord is at hand; it shall come as a destruction from the Almighty. 2 Nephi 23:6

'The day of the Lord' is the day Jehovah comes in judgment. Babylon's fall was one such day, and Latter-day Saints see it as a pattern of the great day when Christ returns.

AttestedProphecy or typeA prophecy of Him

How we know: the chapter heading names Him

alluded to by D&C 133:14 — The Lord commands, 'Go ye out from Babylon', making Babylon the wicked world before His coming.

Signs of His Coming

Behold, the day of the Lord cometh, cruel both with wrath and fierce anger, to lay the land desolate; and he shall destroy the sinners thereof out of it. 2 Nephi 23:9–11

The darkened sun, moon and stars are signs Jesus Himself named for the time of His Second Coming. On that day the Lord will end pride and wickedness in the world.

AttestedProphecy or typeA prophecy of Him

How we know: the chapter heading names Him

alluded to by Matthew 24:29-30 — Jesus: the sun darkened, the moon not giving her light, then the Son of Man comes.
alluded to by D&C 29:14 — The sun darkened and the moon turned to blood before the Lord's coming.
a parallel account in Isaiah 13:9-11 — The same verses in Isaiah.

Jehovah, merciful to His people

And the wild beasts of the islands shall cry in their desolate houses, and dragons in their pleasant palaces; and her time is near to come, and her day shall not be prolonged. For I will destroy her speedily; yea, for I will be merciful unto my people, but the wicked shall perish. 2 Nephi 23:22

Jehovah speaks in His own voice, promising mercy to His people even as Babylon falls. This line is not in the King James Isaiah; the Book of Mormon preserves the Lord's promise of mercy at the end of the judgment.

AttestedJehovah — the LORDHe speaks in the first person

How we know: the chapter heading names Him

a parallel account in Isaiah 13:22 — The King James verse, which lacks the promise of mercy.