Mishkat al-Masabih #453
Purification
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
وَعَنْ عُمَرَ بْنِ الْخَطَّابِ رَضِيَ اللَّهُ عَنْهُ قَالَ: لَا تَغْتَسِلُوا بِالْمَاءِ الْمُشَمَّسِ فَإِنَّهُ يُورِثُ البرص. رَوَاهُ الدَّارَقُطْنِيّ
‘Umar b. al-Khattab said, “Do not wash in water which has been exposed to the sun, for it produces leprosy.”
Daraqutni transmitted it.
About Mishkat al-Masabih
This hadith is #453 from Mishkat al-Masabih, in the Book of Purification.