The Jews who had returned to the Land of Israel with Ezra and Nehemiah gathered on this day and repented their misdeeds, signing a document in which they committed to trust in G‑d and follow His ways. Among the mitzvot they specified were to refrain from intermarriage and from purchasing produce on Shabbat (Nehemiah 9:1–3; 10:1–32).
Link: The Return to Israel
R. Yaakov Yosef was one of the foremost disciples of the Baal Shem Tov. He was the first one to disseminate the teachings of Chassidut in print, publishing the work Toldot Yaakov Yosef in 1780.
Link: The Rabbi’s Secret Sins
On this day in 5756 (1995), the Ribnitzer Rebbe, Rabbi Chaim Zanvil Abramowitz, passed away. For decades, with great self-sacrifice, he lived a full Chassidic lifestyle under Soviet rule before emigrating to Israel and then the U.S.
The day following a festival is called Isru Chag ("tied to the festival"). Tachnun (confession of sins) and similar prayers are omitted throughout the remainder of the festive month of Tishrei.