Reference for Arakhin 50:10

ומה ראית לרבות את הבן ולהוציא את האח

Why do you choose to include the son and exclude the brother? - I include the son because he arises in his father's place, for the purpose of 'designation',<span class="x" onmousemove="('comment',' Ex. XXI, 9. The designation i.e., betrothal of a Hebrew handmaid to her master. There the son automatically enters into his father's rights.');">³</span>

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