On the day preceding the first Passover seder (or on Thursday morning preceding the seder, when the first seder falls on Motza'ei Shabbat), firstborn sons are commanded to celebrate the Fast of the Firstborn which commemorates the salvation of the Hebrew firstborns. According to Exodus 12:29, God struck down all Egyptian firstborns while the Israelites were not affected. However, it is customary for synagogues to conduct a siyum (ceremony marking the completion of a section of Torah learning) right after morning prayers, and the celebratory meal that follows cancels the firstborn's obligation to fast.
On the day preceding the first Passover seder (or on Thursday morning preceding the seder, when the first seder falls on Motza'ei Shabbat), firstborn sons are commanded to celebrate the Fast of the Firstborn which commemorates the salvation of the Hebrew firstborns. According to Exodus 12:29, God struck down all Egyptian firstborns while the Israelites were not affected However, it is customary for synagogues to conduct a siyum (ceremony marking the completion of a section of Torah learning) right after morning prayers, and the celebratory meal that follows cancels the firstborn's obligation to fast.