According to one account in the Midrash, on the 13th of Nissan of the year 2048 from creation (1714 BCE), G-d appeared to Abram, changed his name to Abraham ("father of a multitude of nations") and commanded him to circumcise himself and all members of his household--and all future descendents at the age of eight days--so that "My covenant (brit) shall be in your flesh, as an eternal covenant." Abraham was 99 years old at the time, and his son Ishmael, 13. (Isaac, who was born a year later, was the first Jew to be circumcised at eight days).
Link: More on the Covenant of Circumcision
In the 12th year of his reign (357 BCE), King Achashverosh of Persia endorsed Haman's plan "to destroy, kill and annihilate all Jews, from young to old, infants and women, on a single day, on the 13th day of the 12th month, the month of Adar." On Nissan 13 (11 months before the date chosen for the massacre) proclamations of the decree were drafted and dispatched to all 127 countries of the Persian Empire. Mordechai told Esther to go before the king and plead for her people. Esther asked that a three-day fast be proclaimed (Nissan 14, 15 and 16--including the first two days of Passover) in which all Jews would repent and pray for the success of her mission.
Links:
The Story of Purim
Timeline of the events connected with the Purim miracle
Nissan 13 is the anniversary of the passing of Rabbi Joseph Caro (1488-1575), author of the Shulchan Aruch ("Code of Jewish Law").
Link: Original Ideas
The rabbi of the mystical city of Tzefat, Rabbi Moshe Alshich left an indelible mark on the world of Torah scholarship, both as a master of halachah (Jewish law) and derush (Biblical homily). He passed away in the year 5360 (1600) at a ripe old age and is buried in the ancient cemetery of Tzefat.
Links:
A Brief Biography of the Alshich
A Responsa of the Alshich
Homiletic Teachings of the Alshich
The third Rebbe of Chabad, Rabbi Menachem Mendel Schneersohn of Lubavitch (1789-1866; known as the "Tzemach Tzeddek" after his Halachic work by that name), passed away on Nissan 13.
Links:
A short biography
More on the Tzemach Tzeddek
After reading the "Nasi" describing the gifts brought by the princes of the 12 Tribes of Israel for the dedication of the Tabernacle during the first 12 days of Nissan (see "Nasi of the Day" in Nissan 1), today we read the passage (the opening verses of the Torah portion of Bahaalotecha) describing G-d's instructions to Aaron regarding the lighting of the Menorah, which represents the contribution of the "13th tribe" of Levi.
The Torah (Exodus 12:15, as per Talmud, Pesachim 5a) sets midday of Nissan 14 (tomorrow) as the deadline for the destruction and/or removal of all leavened foods ("chametz") from our possession in preparation for the festival of Passover, which begins tomorrow evening at nightfall. In practice, Torah law mandates that we desist from eating chametz two hours before midday of Nissan 14, and that no leaven remain in our possession an hour before midday. These are not clock hours but "proportional hours", defined by Jewish law as a 12th part of the time between sunrise and sunset.
Chametz is disposed of by: a) selling it to a non-Jew; b) burning the chametz that isn't sold or otherwise disposed of--particularly the chametz found in the "search for chametz" (see Laws and Customs for yesterday, Nissan 12); c) "nullifying" the chametz that hasn't been found by declaring it ownerless.
When Nissan 14 falls on Shabbat--as it does this year--this greatly complicates the process of getting rid of chametz. Neither the search nor the burning of the chametz can take place on the Shabbat. Also the selling of the chametz and the preparation of the Passover kitchen must be done before Shabbat. On the other hand, we need to leave some chametz for the Friday evening and Shabbat morning meals, which each requires two challah loaves.
Thus: the search for chametz is moved ahead to Thursday evening. On Friday morning, we burn the chametz found in the search, leaving behind only the exact amount of chametz that will used for the Shabbat meals. Click here for the chametz burning deadline for your location.
See Laws and Customs for tomorrow, Nissan 14, for more information on the chametz eating deadline and the nullification of the chametz.
For more detailed instructions, see the Getting-Rid-of-Chametz Wizard.