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.
Jewish Publication Society of America Version (JPS1917) - Exodus 13:15 >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 first-born of man, and the first-born of beast; therefore I sacrifice to the LORD all that openeth the womb, being males; but all the first-born of my sons I redeem.