Original sentence: Easter Sunday and Pentecost correspond to pre-existing Jewish feasts
Edited sentence: Easter Sunday and Pentecost correspond to pre-existing Jewish feasts: The first day of Pesach (פסח) and the holiday of Shavu'ot (שבועות).In the Jewish tradition, the 49 days between these holidays are knows as Counting of the Omer (ספירת העומר)‎