God set aside specific seasons He calls “Holy” and we are commanded to honor Him by observing these specific seasons He has appointed, and then He releases blessing because of our obedience.
Fall Feasts of the Lord:
The Feast of Trumpets (or Rosh Hashanah September 6th),
The Day of Atonement (or Yom Kippur September 16th),
The Feast of Tabernacles (Sukkot September 20th-27th)

God commanded His people to honor these “holy days” forever, as an everlasting covenant with Him: They are HIS Holy Days! “Be careful to celebrate the Day of Atonement on the tenth day of that same month—nine days after the Festival of Trumpets. You must observe it as an official day for holy assembly, a day to deny yourselves and present special gifts to the LORD” (Leviticus 23:27 NLT).