As Moses and the Israelites were fleeing Egypt, Pharaoh’s armies pursued them as they were encamped by the sea. Moses held out his hand over the sea and the Lord drove back the sea, allowing the Israelites to pass, but drowned the Egyptians.

There is a Midrash that tells of God rebuking His angels for rejoicing as the Egyptians were drowning, saying, “Are these not my children also?”

We now pour ten drops of wine to symbolize the ten plagues upon Egypt. A full cup of wine is the symbol of complete joy. Though we celebrate our freedom, our cup cannot be filled because our freedom did not come without a cost. Each drop of wine that we pour out of our cups diminishes our joy.

haggadah Section: Introduction
Source: Telling the Story: A Passover Haggadah Explained