여호수아 22:15의 미드라쉬

And it shall be when thy son asketh thee tomorrow: “What is this?” (Exod. 13:14). Sometimes tomorrow means the next day, and sometimes it means the time to come. In the verse When thy son asketh thee tomorrow saying: “What is this?”, tomorrow means in the time to come. But the verse Tomorrow shall this sign be (Exod. 8:19) actually refers to the next day. In the verse Tomorrow will I stand upon the top of the hill (ibid. 17:9), tomorrow refers to the next day, but the verse Tomorrow your children might speak unto our children (Josh. 23:24) refers to the time to come. What is this? This refers to the laws of Passover. And it came to pass, when Pharaoh would hardly let us go (Exod. 13:15). One might understand this to mean that he became hardened of his own accord, therefore Scripture says: And the Lord hardened the heart of Pharaoh (ibid. 9:12). That the Lord slew all the firstborn (ibid. 13:15). From this they taught: The firstlings of cattle are sacrificed because of what happened to the firstborn men in Egypt, and the firstborn of man is redeemed because of what happened to the firstborn of cattle in Egypt.