Numbers 10:7

When calling the assembly together, you are to sound long blasts, not short ones.

Joel 2:1

Blow the horn in Zion;
sound the alarm on My holy mountain!
Let all the residents of the land tremble,
for the Day of the Lord is coming;
in fact, it is near—

Numbers 10:3-4

When both are sounded in long blasts, the entire community is to gather before you at the entrance to the tent of meeting.

Treasury of Scripture Knowledge

Summary

But when the congregation is to be gathered together, ye shall blow, but ye shall not sound an alarm.

Ye shall blow

Sound

Bible References

Ye shall blow

Numbers 10:3
When both are sounded in long blasts, the entire community is to gather before you at the entrance to the tent of meeting.

Sound

Joel 2:1
Blow the horn in Zion;
sound the alarm on My holy mountain!
Let all the residents of the land tremble,
for the Day of the Lord is coming;
in fact, it is near—

Holman Christian Standard Bible®, Copyright © 1999, 2000, 2002, 2003, 2009 by Holman Bible Publishers.