Reference for Arakhin 55:30

אם לגבוה אין אדם רשאי כו':

OR HIS HEBREW MANSERVANT OR MAIDSERVANT, OR THE FIELD WHICH HE ACQUIRED BY PURCHASE, THEY ARE NOT CONSIDERED [VALIDLY] DEVOTED, FOR NONE CAN DEVOTE A THING WHICH DOES NOT BELONG TO HIM.

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