Parashas Ki Sisa · Passuk 34:20
Torah Temimah points to classical source on this unit (verified).
English: “The firstborn of a donkey you shall redeem with a sheep” — redemption of the donkey’s firstborn.
Derash on redeeming the firstborn donkey and the human firstborn.
The firstborn of a donkey you shall redeem with a sheep; if you do not redeem it, you shall break its neck. Every firstborn of your sons you shall redeem. And they shall not appear before Me empty-handed.