Joel 2:15 Blow the trumpet in Zion; consecrate a fast; call a solemn assembly; gather the people. Consecrate the congregation; assemble the elders; gather the children, even nursing infants. Let the bridegroom leave his room, and the bride her chamber. Between the vestibule and the altar let the priests, the ministers of the Lord, weep and say, “Spare your people, O Lord, and make not your heritage a reproach, a byword among the nations. Why should they say among the peoples, ‘Where is their God?’”
The trumpet horn was used to awaken the people as well, to arouse them to get moving. Many places we hear of the trumpet being used to signal the armies into battle. The sound of the trumpet meant; “now we start”, “now we begin”, and for every man to fight with all their strength for their lives and the lives of their families. All of the Jewish people knew that at the sound of the trumpet they all started as one unified unit. Everyone knew their place and what they had to attack or defend. Here we see Joel using the “Trumpet” as a call to urgently gather as one before God and seek His forgiveness and withdrawal of His judgment upon them. The urgency in his prophecy is fully evident. Elders, children, nursing infants, bridegroom, and bride are all to listen and urgently and humbly come before God with pleas of healing their land. Joel had previously called the people to return to God and repent of their disobedience. This call to sound the trumpet seals the call to return and repent with humble repentant hearts. The trumpet call does no good to those who will not react to its sound. It does no good to those who reject the thought of humbly coming before God. It does no good to those who reject the thought of God being in control and can reverse the course of their trials and troubles. But to those who hear the sound and humbly come before God with repentant hearts, they will see His mighty hand at work with renewed hope and trust.