The Shabbat that falls between Rosh Hashanah and Yom Kippur is called Shabbat Shuvah, or the Sabbath of return. If that word reminds you of the word teshuvah, that’s not a coincidence — they share a common root.
Teshuvah, or repentance, is a core concept of the High Holidays. The word literally means “return.” Services on Shabbat Shuvah are typically solemn and focused. And the Haftarah portion deals with themes of repentance and forgiveness.
Ashkenazi Jews read Hosea 14:2-10 and Joel 2:15-27, while Sephardic Jews read Hosea 14:2-10 and Micah 7:18-20. The selection from Hosea focuses on a universal call for repentance and an assurance that those who return to God will benefit from divine healing and restoration. The selection from Joel imagines a blow of the shofar that will unite the people in fasting and supplication. Hosea focuses on divine forgiveness and how great it is in comparison to the forgiveness of man.
Historically, Shabbat Shuvah was also a time when the rabbi of the community would present a special sermon to the congregation. Though this is done every week in most contemporary communities, in previous eras a rabbi’s sermon was expected only twice a year: on Shabbat Shuvah and on Shabbat Hagadol, the intermediate Shabbat of Passover. Sermons on Shabbat Shuvah traditionally focus on themes of repentance, prayer, and charity.