“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 comes, for it is close at hand:”

The people of God are asleep and insensible to what is coming against them. They do not see nor read the signs in the circumstances of life, and so the trumpet of God will sound against them from the holy hill of Zion, the place where God dwells. As the priests sound the trumpet to call the people to repentance, so the trumpet of God is sounded at the coming tragedy, not of locusts, but of final and irrevocable judgment. It is not a trumpet of rejoicing but of wild alarm. It is to awaken the people and warn them of the coming doom, the impending day that will bring judgment and sorrow on them, for they are lost and without hope of salvation.

They have slept away their chances and have not been faithful, to the Lord or paid attention to the warning He has sent them, so now they face the day of His great wrath with no Saviour to mediate for them. They are in the worst possible state. 

The mention here in this verse of the day of the Lord, refers not just to the tragedy of the destruction of the locusts and the famine they bring, but the day of reckoning when the souls of the people will be judged. The day has now come, a day in the future when all will give account for the deeds done in the body. The great day of his wrath is coming and the judgment will be poured out, not in love but in great anger against all the enemies of God, who reject His holy laws and the provision of His salvation offered to all people. 

“Neither their silver nor their gold will be able to deliver them in the day of the Lord’s wrath, but the whole land will be devoured by the fire of his jealousy; for he will make an end, yes, a terrible end, of all those who dwell in the land.”

Zephaniah 1:18

The day of the Lord will surely come, as the other days that were foretold by the prophets. There will be no recompense on the last great day, but all will face their judgment and the Lord will make an end to all evil and evil doers.