Charles Ellicott Commentary Exodus 12:27

"that ye shall say, It is the sacrifice of Jehovah`s passover, who passed over the houses of the children of Israel in Egypt, when he smote the Egyptians, and delivered our houses. And the people bowed the head and worshipped." — Exodus 12:27 (ASV)

It is the sacrifice of the Lord’s passover. —Hebrew, This is a passover-sacrifice to Jehovah. The emphatic word is “Passover”; and it was the meaning of this term which was especially to be explained. The explanation would involve a historical account of the circumstances of the institution, such as would be apt to call forth feelings of gratitude and devotion.