Heifer: when Used As Sacrifice, Must be Without Blemish and Must not Have Come Under the Yoke
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Numbers 19:2
“This is the statute of the law that the LORD has commanded: Instruct the Israelites to bring you an unblemished red heifer that has no defect and has never been placed under a yoke.
Deuteronomy 21:3
Then the elders of the city nearest the victim shall take a heifer that has never been yoked or used for work,