Rabbi Avraham Chaim Na'eh (1890-1954) was born in Hebron to Rabbi Menachem Mendel Na'eh, a Lubavitcher chassid and dean of the Magen Avot, a yeshiva founded by the S'dei Chemed. With the outbreak of World War One, the Ottomans, who controlled the Land of Israel at the time, expelled anyone who was not a citizen of the empire. Most of the exiled Jews, including Rabbi Avraham Chaim, gathered in Alexandria, Egypt. During his time there, Rabbi Avraham Chaim founded Yeshivat Eretz Yisrael and wrote the halachic work Shenot Chaim, a concise digest of halachah for Sephardic Jews. In 1918, he returned to Palestine to work for the Edah HaChareidit (a prominent Orthodox communal organization), under Rabbi Yosef Chaim Sonnenfeld.
Rabbi Na'eh best known for his halachic works Ketzot ha-Shulchan and Shiurei Torah ("measurements of the Torah"), in which he converted halachic measurements into modern terms. Contemporary halachic authorities follow his measurements to this day.
During the Three Weeks, from 17th of Tamuz to the 9th of Av, we commemorate the conquest of Jerusalem, the destruction of the Holy Temple and the dispersion of the Jewish people.
Weddings and other joyful events are not held during this period; like mourners, we do not cut our hair, and various pleasurable activities are limited or proscribed. (The particular mourning customs vary from community to community, so consult a competent halachic authority for details.)
Citing the verse (Isaiah 1:27) "Zion shall be redeemed with mishpat [Torah] and its returnees with tzedakah," the Rebbe urged that we increase in Torah study (particularly the study of the laws of the Holy Temple) and charity during this period.
Links:
The Three Weeks
As long as we search for G‑d by abandoning the world He has made, we can never truly find Him.
As long as we believe there is a place to escape, we cannot be liberated.
The ultimate liberation will be when we open our eyes to see that everything is here, now.