Leviticus 23:24
22 When you gather in the harvest of your land, you must not completely harvest the corner of your field, and you must not gather up the gleanings of your harvest. You must leave them for the poor and the resident foreigner. I am the Lord your God.’” 23 The Lord spoke to Moses: 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. 25 You must not do any regular work, but you must present a gift to the Lord.’” 26 The Lord spoke to Moses:
Psalm 81:3
1 For the music director, according to the gittith style; by Asaph. Shout for joy to God, our source of strength! Shout out to the God of Jacob! 2 Sing a song and play the tambourine, the pleasant-sounding harp, and the ten-stringed instrument. 3 Sound the ram’s horn on the day of the new moon and on the day of the full moon when our festival begins. 4 For observing the festival is a requirement for Israel; it is an ordinance given by the God of Jacob. 5 He decreed it as a regulation in Joseph, when he attacked the land of Egypt. I heard a voice I did not recognize.
Notes and References
"... Leviticus 23:23-25: Beginning with the Feast of Trumpets, regulations regarding the fall festivals are given. During the seventh month four additional Sabbaths were to be observed, which underscores the solemnity of this sacred month in the Israelite worship calendar. The one-day celebration of the Feast of Trumpets was to occur on the first day of the seventh month in which no work was to be done and an offering was made to the Lord. The day was accompanied by trumpet blasts. (In Israel and in the Ancient Near East trumpet blasts were used to assemble masses of people for mass migration or for battle. It has been suggested that they were blown on the first of every month; compare Psalm 81:3) The Feast of Trumpets occurred on the first day of the seventh month and marked the end of one agricultural year and the beginning of another one. The offerings that accompanied this feast are given in Numbers 29:1–6 ..."
Rooker, Mark F. The New American Commentary: Leviticus (pp. 245-246) Broadman & Holman, 2000