The Scofield Bible Commentary, by Cyrus Ingerson Scofield, [1917], at sacred-texts.com
that the mountain
A mountain, in Scripture symbolism, means a kingdom (Dan 2:35); (Rev 13:1); (Rev 17:9-11).
Day of the Lord
(Day of Jehovah) vs.
(Isa 2:10-22); (Isa 4:1-6); (Isa 11:10-13); (Isa 13:9-16); (Isa 24:21-23); (Isa 26:20); (Isa 26:21); (Isa 63:1-6); (Isa 66:15-24); (Jer 25:29-33); (Isa 46:10); (Eze 30:3); (Rev 19:11-21).