Albert Barnes Commentary Leviticus 23:24

"Speak unto the children of Israel, saying, In the seventh month, on the first day of the month, shall be a solemn rest unto you, a memorial of blowing of trumpets, a holy convocation." — Leviticus 23:24 (ASV)

A sabbath - Here and in (Leviticus 23:39), it is a word that should rather be rendered a sabbatical rest.

Blowing of trumpets - Here and in (Numbers 29:1), this literally means “shouting.” There is no mention of trumpets in the Hebrew text of the Law in connection with this day.

However, there is no reason to doubt the tradition that the day was distinguished by a general blowing of trumpets throughout the land, and that the kind of trumpet generally used for the purpose was the curved horn of an animal or a cornet of metal, such as was used at Sinai (Exodus 19:16) and on the Day of Jubilee (Leviticus 25:9).

It must have differed in this respect from the ordinary festival of the New Moon, when the long, straight trumpet of the temple alone was blown (Numbers 10:2; Exodus 25:23).

Seventh month - This month was called Tisri by the Jews in later times, but in the Old Testament it is called Ethanim (1 Kings 8:2). According to the uniform voice of tradition, “the first day” of this month was the first day of the Civil Year in use before the Exodus and was observed as the festival of the New Year. Some have viewed it as a commemoration of the creation of the world (Job 38:7): others, as the anniversary of the giving of the Law.