Numbers 6:12

6:12 He must rededicate to the Lord the days of his separation and bring a male lamb in its first year as a reparation offering, but the former days will not be counted because his separation was defiled.

Numbers 7:87

7:87 All the animals for the burnt offering were 12 young bulls, 12 rams, 12 male lambs in their first year, with their grain offering, and 12 male goats for a purification offering.

Numbers 8:16

8:16 For they are entirely given to me from among the Israelites. I have taken them for myself instead of all who open the womb, the firstborn sons of all the Israelites.