Sayyiduna Abu Sa'id (may Allah be pleased with him) says: Two men disputed over a date palm. The Prophet (peace and blessings be upon him) cut one of its fronds and measured with it, and found it to be five (cubits), so he made that its surrounding boundary.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب إحياء الموات / 11864