Exodus 13:15

Overview - Exodus 13
1	The firstborn are sanctified to God.
3	The memorial of the passover is commanded.
11	The firstlings of man and beast are set apart.
17	The Israelites go out of Egypt, and carry Joseph's bones with them.
20	They come to Etham.
21	God guides them by a pillar of a cloud, and a pillar of fire.

Exodus 13:15  (King James Version)
And it came to pass, when Pharaoh would hardly let us go, that the LORD slew all the firstborn in the land of Egypt, both the firstborn of man, and the firstborn of beast: therefore I sacrifice to the LORD all that openeth the matrix, being males; but all the firstborn of my children I redeem.