Ta'anit Bechorim - Fast of the First Born
The Fast of the Firstborn (Ta’anit B’Chorim) commemorates the horrific tenth plague that God inflicted on Pharoah and the Egyptian people. After Pharoah had again refused to let the Children of Israel go, Moses warned of the impending plague that would see the death of every first-born son in the land.
The sons of the Israelites were spared because their families sacrificed a lamb and put some of its blood on the doorposts of their homes, allowing the Angel of Death to ‘pass over’ the Jewish homes. This is where the English name ‘Passover’ for the festival Pesach comes from.
In thanksgiving for their survival, the first-born son in a Jewish family fasts from dawn on Erev Pesach until the Pesach Seder. If a simcha (happy occasion) such as a betrothal or the completion of study of a tractate of Talmud falls on Erev Pesach, the fast is excused and the first-born sons present are exempt from fasting.
Links:
Chabad.org: The Fast of the First Born
Akhlah: Ta'anit Bechorot
My Jewish Learning: The Fast of the First Born
