Reference for Bekhorot 101:8

תנא

I might have thought that since shekalim is not written in connection with these cases<span class="x" onmousemove="('comment',' There being no mention in the Torah that the payment must be in shekels. And although the Mishnah does not mention the holy shekel in connection with the other cases enumerated, the word shekel is used in the Scriptures with reference to them. In connection with the first-born Scripture says, Five shekels by the poll (Num. III, 47) . With reference to a Slave it says: He shall give the master thirty shekels. (Ex. XXI, 32) . And kueah with reference to seduction it says: He shall pay silver () . (Ex. XXII, 16) .');">⁴</span>

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