Numbers 3:41

Overview - Numbers 3
1	The sons of Aaron.
5	The Levites are given to the priests instead of the first-born;
14	are numbered by their families.
21	The families, number, and charge of the Gershonites;
27	of the Kohathites;
33	of the Merarites.
38	The place and charge of Moses and Aaron.
40	The first-born are freed by the Levites.
44	The overplus are redeemed.

Numbers 3:41  (King James Version)
And thou shalt take the Levites for me (I am the LORD) instead of all the firstborn among the children of Israel; and the cattle of the Levites instead of all the firstlings among the cattle of the children of Israel.