Exodus:34:19-20
web@Exodus:34:19 @ "All that opens the womb is mine; and all your livestock that is male, the firstborn of cow and sheep.
web@Exodus:34:20 @ The firstborn of a donkey you shall redeem with a lamb: and if you will not redeem it, then you shall break its neck. All the firstborn of your sons you shall redeem. No one shall appear before me empty.