Sayyidah Aishah (may Allah be pleased with her) narrates: The Prophet (peace and blessings be upon him) would pray even at a place where Sayyiduna Hasan (may Allah be pleased with him) or Sayyiduna Husayn (may Allah be pleased with him) had urinated, and he said: "When a servant performs one prostration for Allah Almighty, Allah Almighty purifies the place of his prostration down to the seven earths."
Imam al-Tabarani recorded it in al-Mu'jam al-Awsat, and the narrator Buzaygh has been accused of fabricating hadith.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1932