Leviticus 23:24

23:24 “Tell the Israelites, ‘In the seventh month, on the first day of the month, you must have a complete rest, a memorial announced by loud horn blasts, a holy assembly.

Leviticus 25:9

25:9 You must sound loud horn blasts – in the seventh month, on the tenth day of the month, on the Day of Atonement – you must sound the horn in your entire land.