Muwatta Malik #106
Purity
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ عَبْدِ اللَّهِ بْنِ كَعْبٍ، مَوْلَى عُثْمَانَ بْنِ عَفَّانَ أَنَّ مَحْمُودَ بْنَ لَبِيدٍ الأَنْصَارِيَّ، سَأَلَ زَيْدَ بْنَ ثَابِتٍ عَنِ الرَّجُلِ، يُصِيبُ أَهْلَهُ ثُمَّ يُكْسِلُ وَلاَ يُنْزِلُ فَقَالَ زَيْدٌ يَغْتَسِلُ . فَقَالَ لَهُ مَحْمُودٌ إِنَّ أُبَىَّ بْنَ كَعْبٍ كَانَ لاَ يَرَى الْغُسْلَ . فَقَالَ لَهُ زَيْدُ بْنُ ثَابِتٍ إِنَّ أُبَىَّ بْنَ كَعْبٍ نَزَعَ عَنْ ذَلِكَ قَبْلَ أَنْ يَمُوتَ .
Yahya related to me from Malik from Yahya ibn Said from Abdullah
ibn Kab, the mawla of Uthman ibn Affan that Mahmud ibn Labid al-Ansari
asked Zayd ibn Thabit about a man who penetrated his wife but became
listless and did not ejaculate. Zayd ibn Thabit said, "He does ghusl."
Mahmud said to him, "Ubayy ibn Kab used not to think that ghusl was
necessary," but Zayd ibn Thabit said, "Ubayy ibn Kab drew away from
that before he died."
About Muwatta Malik
This hadith is #106 from Muwatta Malik, in the Book of Purity.