It is narrated from Sayyiduna Abdullah bin Mughaffal (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever digs a well, it is not permissible for anyone else to dig a well within forty cubits around it for watering and resting their animals (i.e., the area of forty cubits around the well should be left for the one who dug it)."
Hadith Referenceسنن دارمي / من كتاب البيوع / 2662
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):إسناده فيه علتان: ضعف إسماعيل بن مسلم وعنعنة الحسن، [مكتبه الشامله نمبر: 2668]
Hadith Takhrijاس روایت کی سند میں اسماعیل بن مسلم ضعیف ہیں اور حسن کا عنعنہ ہے لیکن اس کا شاہد موجود ہے۔ تفصیل کے لئے دیکھئے: [ابن ماجه 2486] ، [مجمع الزوائد 6705] ، [نصب الراية 291/4] ، [تلخيص الحبير 63/3] ، [البيهقي 155/6] ، [المستدرك 97/4]
Brief Explanation
(Commentary on Hadith 2661)
The meaning of the chapter heading "Hareem al-Bir" is that if someone digs a well, how much area around it must be left vacant for seating animals and for giving them water to drink.
From the aforementioned hadith, it is established that forty hands (cubits) must be left on each side around it.
Some scholars have said that this applies when the depth of the well is forty hands.
Allamah Waheed al-Zaman writes in his Sharh Ibn Majah that some ignorant Hanafis, who have absolutely no knowledge of hadith, have deduced from this hadith that a ten-by-ten (10/10) hand pond will not become impure if impurity falls into it. However, this meaning is not derived from the hadith at all. Even if someone were to forcibly extract such a meaning, it would necessitate that the Hanafis should stipulate a forty-by-forty (40/40) hand pond, not ten-by-ten, because in this hadith, forty hands are mentioned on every side.