Water; Its Purity and Impurity
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 2
وَ سَأَلَ عَلِيُّ بْنُ جَعْفَرٍ أَخَاهُ مُوسَى بْنَ جَعْفَرٍ عَلَيْهِ اَلسَّلاَمُ عَنِ اَلرَّجُلِ اَلْجُنُبِ هَلْ يُجْزِيهِ عَنْ غُسْلِ اَلْجَنَابَةِ أَنْ يَقُومَ فِي اَلْمَطَرِ حَتَّى يُغْسَلَ رَأْسُهُ وَ جَسَدُهُ وَ هُوَ يَقْدِرُ عَلَى مَاءٍ سِوَى ذَلِكَ فَقَالَ «إِذَا غَسَلَهُ اِغْتِسَالَهُ بِالْمَاءِ أَجْزَأَهُ ذَلِكَ.
Ali ibn Ja'far asked his brother Imam Musa ibn Jafar Al-Kadhim عليه السلام about a man in a state of major ritual impurity (junub) : Would it suffice for him to stand in the rain until his head and body are washed, if he also has access to other water? Imam عليه السلام said: "If the rain washes him completely as it would with water for ghusl, then that suffices."
- Ṣaḥīḥ al-Faqīh