Muwatta Malik, Book 2, Hadith 89 (USC-MSA)

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to sweat in a garment while he was junub and then pray with it on.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَعْرَقُ فِي الثَّوْبِ وَهُوَ جُنُبٌ ثُمَّ يُصَلِّي فِيهِ ‏.‏

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also referenced under: Book 2, Hadith 119 (In-Book)