Pesach begins on the 15th day of the Jewish month of Nissan. It is the first of the three major festivals with both historical and agricultural significance (the other two are Shavu'ot and Sukkot). Agriculturally, it represents the beginning of the harvest season in Israel, but little attention is paid to this aspect of the holiday. The primary observances of Pesach are related to the Exodus from Egypt after generations of slavery. This story is told in Exodus, Ch. 1-15. Many of the Pesach observances are instituted in Chs. 12-15.


This is what I found on several sites and it has always been my understanding of it...