Sahih al-Bukhari, Hadith 239

The same narrator said that the Prophet had said: "You should not pass urine in stagnant water which is not flowing then (you may need to) wash in it."

وَبِإِسْنَادِهِ قَالَ ‏ "‏ لاَ يَبُولَنَّ أَحَدُكُمْ فِي الْمَاءِ الدَّائِمِ الَّذِي لاَ يَجْرِي، ثُمَّ يَغْتَسِلُ فِيهِ ‏" ‏‏.‏

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