And the Lord spake unto Moses Continued to speak unto him, and give him the reason of his appointing the Levites to minister to the priests and serve the tabernacle:
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"Out of all the Israelites, I have taken the Levites to be substitutes for every firstborn male offspring among them. The Levites are mine,
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because every firstborn is mine. The day I killed every firstborn male in Egypt, I set apart as holy every firstborn in Israel, whether human or animal. They will be mine. I am the LORD."