Theme: Parting the Red Sea. The word “Parting” (Unclued 37-Across) literally parts “Red” (Unclued 36-Across) and “Sea (Uncluded 39-Across). Other related answers are found throughout the grid.
19A. Leader of a noted 37-Across = Moses
25A. Feast of unleavened bread = Pesach (the Hebrew word for Passover)
54A. Location of 37-Across = Egypt
11D. Beneficiary of the 37-Across, in modern times = Israeli
41D. Loser on account of the 37-Across = Pharoah