Numbers 3:12

3:12 “Look, I myself have taken the Levites from among the Israelites instead of every firstborn who opens the womb among the Israelites. So the Levites belong to me,

Numbers 3:40

The Substitution for the Firstborn

3:40 Then the Lord said to Moses, “Number all the firstborn males of the Israelites from a month old and upward, and take the number of their names.

Numbers 3:43

3:43 And all the firstborn males, by the number of the names from a month old and upward, totaled 22,273.

Numbers 26:5

Reuben

26:5 Reuben was the firstborn of Israel. The Reubenites: from Hanoch, the family of the Hanochites; from Pallu, the family of the Palluites;

Numbers 33:4

33:4 Now the Egyptians were burying all their firstborn, whom the Lord had killed among them; the Lord also executed judgments on their gods.