Albert Barnes Commentary Joel 2:16

"gather the people, sanctify the assembly, assemble the old men, gather the children, and those that suck the breasts; let the bridegroom go forth from his chamber, and the bride out of her closet." — Joel 2:16 (ASV)

Sanctify the congregation – “Do what is in your power, by admonishing, exhorting, threatening, giving the example of a holy life, so that the whole people present itself holy before its God,” “so that your prayers are not hindered, and a little leaven does not corrupt the whole lump.”

Assemble the elders – “The judgment concerned all; all then were to join in seeking mercy from God. None were on any pretext to be exempted; not the oldest, whose strength had decayed, or the youngest, who might seem not yet strong enough.” The old also are commonly freer from sin and more given to prayer.

Gather the children – “He who feeds the young ravens when they cry will not neglect the cry of poor children. He assigns as a reason why it was fitting to spare Nineveh, the six-score thousand persons that could not discern between their right hand and their left (Jonah 4:11).

The sight of those who were involved in their parents’ punishment could not help but move the parents to greater earnestness. So when Moab and Ammon (2 Chronicles 20:1–4, 13), a great multitude, came against Jehoshaphat, he proclaimed a fast throughout all Judah, and Judah gathered together to ask help of the Lord; even out of all the cities of Judah, they came to seek the Lord.

And all Judah was standing before the Lord, their little ones also, their wives, and their children.” So it is described in the book of Judith how with great vehemence did they humble their souls, both they and their wives and their children—and every man and woman and the little children—fell before the temple, and cast ashes upon their heads and spread out their sackcloth before the Face of the Lord .

Let the bridegroom go forth – He does not even say the married, or the newly married, or one who had taken a new wife, but he uses the special terms of the wedding day, bridegroom and bride.

The newly married man was, for a year, exempted from going out to war or from any duties that might press upon him (Deuteronomy 24:5). But nothing was to exempt from this common affliction of sorrow.

Even the newly married couple, even if it were the very day of their wedding, were to leave the marriage chamber and join in the common austerity of repentance. It was a mockery of God to spend in delights the time He had consecrated to sorrow.

He says, In that day did the Lord God of hosts call to weeping, and to mourning, and to baldness, and to girding with sackcloth. And behold joy and gladness—surely this iniquity shall not be purged from you until ye die, saith the Lord God of Hosts (Isaiah 22:12–14).

Therefore, in times of fasting or prayer, the Apostle suggests giving up pure pleasures, that ye may give yourselves to fasting and prayer (1 Corinthians 7:5).

“He then who, by chastisement in food and by fasting and alms, says that he is doing acts of repentance, in vain does he promise this in words, unless he goes forth out of his chamber and fulfills a holy and pure fast by chaste penitence.”