Fast of the 17th of Tammuz: Historical Background & Customs

 https://www.ou.org/holidays/the_17th_of_tammuz1/

The 17th day in the Jewish month of Tammuz, Jews the world over fast and lament to commemorate the many calamities that have befallen our people on this ominous day.

The purpose of such fasts in the Jewish calendar is, according to Rabbi Eliyahu Kitov’s Book of Our Heritage, “to awaken hearts towards repentance through recalling our forefathers’ misdeeds; misdeeds which led to calamities…”

Other interesting occurrences on this day include Noach sending out the first dove to see if the Flood waters had receded, (Bereishit 8:8) in 1650 (2100 BCE); Moshe Rabbeinu destroying the golden calf, (Shemot 32:20, Seder Olam 6, Taanit 30b – Rashi) and then ascending back up Har Sinai for the second time where he spent the next forty days pleading for forgiveness for the sin of the golden calf, (Shemot 33:11, Rashi).