مُوَطَّأُ مَالِكٍ
Muwatta Malik 119
Purity
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَعْرَقُ فِي الثَّوْبِ وَهُوَ جُنُبٌ ثُمَّ يُصَلِّي فِيهِ .
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.
Arabic/English book reference: Book 2, Hadith 89