Reference for Eruvin 40:21

מידי גבי הדדי תניא תנ"ה ר"א אוסר בגמל הואיל וצוארו ארוך

Has not R'Safra in the name of R'Ammi who had it from R'Johanan in fact said: If a man was removing his things from one corner into another and then changed his mind and carried them out [into a public domain] he is exempt, since the lifting up [of the objects] was not originally intended for this purpose? - Rather, [this is the explanation:] Sometimes he might, after he had repaired the manger, carry [the bucket] back again, and would thus carry from the public into a private domain. Come and hear: A camel whose head and the greater part of its body is within [a private domain] may be crammed within [that domain].

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