Page "Passover" Paragraph 48

On the morning of the Passover seder, firstborn sons are commanded to observe 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.