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Ibn Ezra on the Torah
Chapter 4
Genesis 4
CAIN SAID "..." - It seems to me that [Cain] said to [Abel] all of the ways that God had rebuked him. One must have been born on a dismal day to ask the question, "How did he kill him without [the advent of] a sword?" What an astonishing question, since he could have killed him by throttling him with his bare hands, moreover, there were thousands of sticks and rocks about.
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