'Opens' in the Bible

"I'm taking the descendants of Levi for myself from among the Israelis in place of every first-born who opens the womb. The descendants of Levi belong to me

But if the Lord brings about something unprecedented, and the ground opens its mouth and swallows them along with all that belongs to them so that they go down alive into Sheol, then you will know that these men have despised the Lord.”

Everything that opens the womb, any living thing that they bring to the LORD whether from human beings or animals are for you. Just be sure that you redeem the firstborn of people and the firstborn of unclean animals.