King James Version (KJV) Authorized Version 1611
Read Full Chapter (Numbers 3)

Numbers 3:11-13 KJV

"And the LORD spake unto Moses, saying, And I, behold, I have taken the Levites from among the children of Israel instead of all the firstborn that openeth the matrix among the children of Israel: therefore the Levites shall be mine; Because all the firstborn are mine; for on the day that I smote all the firstborn in the land of Egypt I hallowed unto me all the firstborn in Israel, both man and beast: mine shall they be: I am the LORD."
Numbers Chapter 3, Verse 11-13

Numbers 3:11-13 in Context (Verses 8–16 KJV)

8
And they shall keep all the instruments of the tabernacle of the congregation, and the charge of the children of Israel, to do the service of the tabernacle.
9
And thou shalt give the Levites unto Aaron and to his sons: they are wholly given unto him out of the children of Israel.
10
And thou shalt appoint Aaron and his sons, and they shall wait on their priest’s office: and the stranger that cometh nigh shall be put to death.
11
And the LORD spake unto Moses, saying,
12
And I, behold, I have taken the Levites from among the children of Israel instead of all the firstborn that openeth the matrix among the children of Israel: therefore the Levites shall be mine;
13
Because all the firstborn are mine; for on the day that I smote all the firstborn in the land of Egypt I hallowed unto me all the firstborn in Israel, both man and beast: mine shall they be: I am the LORD.
14
¶ And the LORD spake unto Moses in the wilderness of Sinai, saying,
15
Number the children of Levi after the house of their fathers, by their families: every male from a month old and upward shalt thou number them.
16
And Moses numbered them according to the word of the LORD, as he was commanded.*