The Midrash Gen.Rabbah gives three views about the weapon that Cain
used to kill Abel: A stone, a cane (Heb. Kanah, a word similar to
Cain's name), or a sword (because Cain had seen Adam using a sword
to kill a sacrifice). Other Midrashim give variants on these views,
and the Zohar says that Cain used his teeth. The Midrash Rabbah adds
that Cain tried various methods before he found one that worked.
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