Reference for Bekhorot 101:18

לפיכך אם רצה הכהן ליתן לו במתנה רשאי

on account of the burden of the journey.<span class="x" onmousemove="('comment',' Because their gold coins are stamped, but other coins which are unstamped cannot be sent to Jerusalem. And the same limitation applies to money's worth, in case it drops in value and hekdesh will thus suffer a loss.');">¹³</span>

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