Reference for Arakhin 39:59

ת"ר

Now it would make a full gift for one to vow a whole [vessel], but it is not usual to vow only half [a vessel].<span class="x" onmousemove="('comment',' Therefore, if he had evaluated a whole object on the principle that no man utters words in vain, he would have been considered liable. But an unusual gift made in the additionally abnormal form of half of an object must have been meant 'in vain', not seriously. hence the Rabbis decide that he need not pay anything at all.');">¹⁵</span>

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