What did the Feast of Passover commemorate?
The Feast of Passover commemorated the night in Egypt when the death angel flew over and the people were protected by the blood. It was a spring memorial and yearly reminder of that night, observed as one of the Feast Days after Israel came out of Egypt.
Les explains that Passover was the Feast in the Spring, a reminder or memorial of the Night of the Passover in Egypt when the death angel flew over and they were protected by the blood. He notes it was one of the Feast Days that began shortly after Israel came out of Egypt, along with First Fruits and Unleavened Bread. He contrasts it with the Day of Atonement, which was in the Fall and is known in English as Yom Kippur, and says Yom Kippur is a better definition than Atonement because the English word is a misnomer; animal bloods couldn't take away sin.