Albert Barnes 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 — or This is the sacrifice of the Passover to Yahweh.

The most formal and exact designation of the festival is thus given. But “the Passover” may mean either the act of God’s mercy in sparing the Israelites, or the lamb which is offered in sacrifice—more probably the latter, as in (Exodus 12:21). This gives a clear sense to the expression “to Yahweh;” the Passover lamb was a sacrifice offered to Yahweh by His ordinance.