Albert Barnes Commentary Joel 2:1

"Blow ye the trumpet in Zion, and sound an alarm in my holy mountain; let all the inhabitants of the land tremble: for the day of Jehovah cometh, for it is nigh at hand;" — Joel 2:1 (ASV)

Blow you the trumpet - The trumpet was accustomed to sound in Zion only for religious uses: to call together the congregations for holy meetings, and to usher in the beginnings of their months and their solemn days with festival gladness. Now in Zion itself—the stronghold of the kingdom, the Holy City, the place where God chose to put His Name, which He had promised to establish—the trumpet was to be used only for sounds of alarm and fear. Alarm could not penetrate there without having pervaded the whole land. With it, the whole human hope of Judah was gone.

Sound an alarm in My holy mountain - He repeats the warning in varied expressions, in order to impress people’s hearts more and to stir them to repentance. Even “the holy mountain” of God was to echo with alarms; the holiness, once bestowed upon it, was to be no security against the judgments of God. Indeed, it was there that those judgments were to begin. So Peter says, “The time is come, that judgment must begin at the house of God” (1 Peter 4:17). The alarm being blown in Zion, terror was to spread to all the inhabitants of the land, who, in fear, were to repent. The Church of Christ is foretold in prophecy under the names of “Zion” and of the holy “mountain.” It is the “stone cut out without hands, which became a great mountain, and filled the whole earth” (Daniel 2:34–35).

Of it, it is said, “Come you and let us go up to the mountain of the Lord, to the house of the God of Jacob!” (Isaiah 2:3). And Paul says, “You are come unto Mount Zion and unto the city of the living God” (Hebrews 12:22). The words then are a rule for all times. The judgments predicted by Joel represent all judgments until the end; the conduct, prescribed on their approach, is a pattern to the Church at all times.

As one commentator notes: “In this mountain we must wail, considering the failure of the faithful, in which, “iniquity abounding, charity waxeth cold.” For now (1450 A.D.) the state of the Church is so sunken, and you may see so great misery in her from the most evil conduct of many, that one who burns with zeal for God, and truly loves his brothers, must say with Jeremiah, “Let mine eyes run down with tears night and day, and let them not cease, for the virgin daughter of my people is broken with a great breach” (Jeremiah 14:17).

Let all the inhabitants of the land tremble - Another comments: “We should be troubled when we hear the words of God rebuking, threatening, and avenging, as Jeremiah says, ‘My heart within me is broken, all my bones shake... because of the Lord, and because of the words of His holiness’ (Jeremiah 23:9). Good is the trouble by which people, weighing their sins, are shaken with fear and trembling, and repent.”

For the Day of the Lord is at hand - “The Day of the Lord” is any day in which He avenges sin, any day of Judgment, in the course of His Providence or at the end: the day of Jerusalem from the Chaldees or Romans, the day of antichrist, the day of general or particular judgment, of which James says, “The coming of the Lord draweth nigh. Behold the Judge standeth before the door” (James 5:8–9). Another writer says: “Well is that called ‘the day of the Lord,’ in that, by the divine appointment, it avenges the wrongs done to the Lord through the disobedience of His people.”