Numbers 18:15

every one opening a womb of all flesh which they bring near to Jehovah, among man and among beast, is thine; only, thou dost certainly ransom the first-born of man, and the firstling of the unclean beast thou dost ransom.

Exodus 34:20

and the firstling of an ass thou dost ransom with a lamb; and if thou dost not ransom, then thou hast beheaded it; every first-born of thy sons thou dost ransom, and they do not appear before Me empty.

Exodus 13:2

Sanctify to Me every first-born, opening any womb among the sons of Israel, among man and among beast; it is Mine.'

Exodus 13:12-13

that thou hast caused every one opening a womb to pass over to Jehovah, and every firstling -- the increase of beasts which thou hast: the males are Jehovah's.

Exodus 22:29

'Thy fulness and thy liquids thou dost not delay; the first-born of thy sons thou dost give to Me;

Leviticus 27:26-27

Only, a firstling which is Jehovah's firstling among beasts -- no man doth sanctify it, whether ox or sheep; it is Jehovah's.

Numbers 3:13

for Mine is every first-born, in the day of My smiting every first-born in the land of Egypt I have sanctified to Myself every first-born in Israel, from man unto beast; Mine they are; I am Jehovah.'

Numbers 3:46

And from those ransomed of the two hundred and seventy and three (who are more than the Levites) of the first-born of the sons of Israel,

Treasury of Scripture Knowledge

Summary

Every thing that openeth the matrix in all flesh, which they bring unto the LORD, whether it be of men or beasts, shall be thine: nevertheless the firstborn of man shalt thou surely redeem, and the firstling of unclean beasts shalt thou redeem.

General references

Bible References

The firstborn

Exodus 13:13
And every firstling of an ass thou dost ransom with a lamb, and if thou dost not ransom it, then thou hast beheaded it: and every first-born of man among thy sons thou dost ransom.
Exodus 34:20
and the firstling of an ass thou dost ransom with a lamb; and if thou dost not ransom, then thou hast beheaded it; every first-born of thy sons thou dost ransom, and they do not appear before Me empty.
Leviticus 27:27
And if among the unclean beasts, then he hath ransomed it at thy valuation, and he hath added its fifth to it; and if it is not redeemed, then it hath been sold at thy valuation.

General references

Numbers 3:15
'Number the sons of Levi by the house of their fathers, by their families; every male from a son of a month and upward thou dost number them.'