15 Blow the trumpet in Zion, declare a holy fast, call a sacred assembly.

Read Joel 2:15 Using Other Translations

Blow the trumpet in Zion, sanctify a fast, call a solemn assembly:
Blow the trumpet in Zion; consecrate a fast; call a solemn assembly;
Blow the ram’s horn in Jerusalem! Announce a time of fasting; call the people together for a solemn meeting.