Leviticus 23:24

Speak unto the children of Israel, saying, In the seventh month, in the first day of the month, shall ye have a sabbath, a memorial of blowing of trumpets, an holy convocation.

A sabbath — Solemnized with the blowing of trumpets by the priests, not in a common way, as they did every first day of every month, but in an extraordinary manner, not only in Jerusalem, but in all the cities of Israel. They began to blow at sun-rise, and continued blowing till sun-set. This seems to have been instituted, 1. To solemnize the beginning of the new year, whereof as to civil matters and particularly as to the Jubilee, this was the first day; concerning which it was fit the people should be admonished, both to excite their thankfulness for God's blessings in the last year, and to direct them in the management of their civil affairs2. To put a special honour upon this month. For as the seventh day was the sabbath, and the seventh year was a sabbatical year, so God would have the seventh month to be a kind of sabbatical month, for the many sabbaths and solemn feasts which were observed in this more than in any other month. And by this sounding of the trumpets in its beginning, God would quicken and prepare them for the following sabbaths, as well as that of atonement and humiliation for their sins, as those of thanksgiving for God's mercies.