Joel 2:1–11 (NKJV)
2:1 Blow the trumpet in Zion, And sound an alarm in My holy mountain! Let all the inhabitants of the land tremble; For the day of the Lord is coming, For it is at hand:
2 A day of darkness and gloominess, A day of clouds and thick darkness, Like the morning clouds spread over the mountains. A people come, great and strong, The like of whom has never been; Nor will there ever be any such after them, Even for many successive generations.
3 A fire devours before them, And behind them a flame burns; The land is like the Garden of Eden before them, And behind them a desolate wilderness; Surely nothing shall escape them.
4 Their appearance is like the appearance of horses; And like swift steeds, so they run.
5 With a noise like chariots Over mountaintops they leap, Like the noise of a flaming fire that devours the stubble, Like a strong people set in battle array.
The Lord instructs the prophet Joel to blow the trumpet to call the people together for a warning. The day of the Lord is coming! He then describes the circumstances of the day: darkness, a cloud, a group of people–strong and great– coming against Israel. A fire will precede them, and they leave the land as a wilderness. They come in chariots and they set up in battle array. The people of Israel are facing the judgment of the Lord as He sends a nation against them.
6 Before them the people writhe in pain; All faces are drained of color.
7 They run like mighty men, They climb the wall like men of war; Every one marches in formation, And they do not break ranks.
8 They do not push one another; Every one marches in his own column. Though they lunge between the weapons, They are not cut down.
9 They run to and fro in the city, They run on the wall; They climb into the houses, They enter at the windows like a thief.
10 The earth quakes before them, The heavens tremble; The sun and moon grow dark, And the stars diminish their brightness.
The Lord then describes the army that will come to attack Israel. They are ferocious and instill fear in all people before them. They are trained and disciplined soldiers, taking out everything in their path. Even nature trembles before them.
11 The Lord gives voice before His army, For His camp is very great; For strong is the One who executes His word. For the day of the Lord is great and very terrible; Who can endure it?
All of this describes the power and authority of God that will be unleashed on the day of the Lord–a day of judgment and recompense. God will not be mocked. He will be respected and worshipped. Do not push God away. Instead, bow before Him!