It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that once someone asked the Prophet Muhammad (peace and blessings be upon him) about this issue: If a person finds water in the wilderness where animals and beasts also come, can he perform ablution with it? I heard that the Prophet Muhammad (peace and blessings be upon him) said: "When the water reaches the amount of two pitchers, impurity does not affect it."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 4803
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن، محمد بن إسحاق صرح بالتحديث عند الدارقطني، فانتفت شبهة تدليسه