It is narrated from Sa'id bin al-Musayyab (may Allah have mercy on him) that the boundary zone of a new well is twenty-five cubits on all its sides, the boundary zone of an ancient well is fifty cubits on all its sides, and the boundary zone of a well for crops is three hundred cubits on all its sides. Al-Zuhri (may Allah have mercy on him) says: I heard people say that the boundary zone of springs is five hundred cubits.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب إحياء الموات / 11869