Joel 2:15

15 Sound the trumpet in Sion, sanctify a fast, proclaim a service:

Joel 2:15 Meaning and Commentary

Joel 2:15

Blow the trumpet in Zion
For the calling of the people together to religious duties, which was one use of the silver trumpets made for and blows by the priests, ( Numbers 10:2 Numbers 10:3 Numbers 10:8 Numbers 10:10 ) ; sanctify a fast, call a solemn assembly; (See Gill on Joel 1:14).

Joel 2:15 In-Context

13 and rend your hearts, and not your garments, and turn to the Lord your God: for he is merciful and compassionate, long-suffering, and plenteous in mercy, and repents of evils.
14 Who knows if he will return, and repent, and leave a blessing behind him, even a meat-offering and a drink-offering to the Lord your God?
15 Sound the trumpet in Sion, sanctify a fast, proclaim a service:
16 gather the people, sanctify the congregation, assemble the elders, gather the infants at the breast: let the bridegroom go forth of his chamber, and the bride out of her closet.
17 Between the porch and the altar let the priests that minister to the Lord weep, and say, Spare thy people, O Lord, and give not thine heritage to reproach, that the heathen should rule over them, lest they should say among the heathen, Where is their God?

Footnotes 1

The Brenton translation of the Septuagint is in the public domain.