Exodus 34:19 in the World English Bible
“All that opens the womb is mine; and all your livestock that is male, the firstborn of cow and sheep.
Context
18 The feast of unleavened bread shalt thou keep. Seven days thou shalt eat unleavened bread, as I commanded thee, in the time of the month Abib: for in the month Abib thou camest out from Egypt.
19 All that openeth the matrix is mine; and every firstling among thy cattle, whether ox or sheep, that is male.
20 But the firstling of an ass thou shalt redeem with a lamb: and if thou redeem him not, then shalt thou break his neck. All the firstborn of thy sons thou shalt redeem. And none shall appear before me empty.