Muwatta Malik #105
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 سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّ أَبَا مُوسَى الأَشْعَرِيَّ، أَتَى عَائِشَةَ زَوْجَ النَّبِيِّ صلى الله عليه وسلم فَقَالَ لَهَا لَقَدْ شَقَّ عَلَىَّ اخْتِلاَفُ أَصْحَابِ النَّبِيِّ صلى الله عليه وسلم فِي أَمْرٍ إِنِّي لأُعْظِمُ أَنْ أَسْتَقْبِلَكِ بِهِ . فَقَالَتْ مَا هُوَ مَا كُنْتَ سَائِلاً عَنْهُ أُمَّكَ فَسَلْنِي عَنْهُ . فَقَالَ الرَّجُلُ يُصِيبُ أَهْلَهُ ثُمَّ يُكْسِلُ وَلاَ يُنْزِلُ فَقَالَتْ إِذَا جَاوَزَ الْخِتَانُ الْخِتَانَ فَقَدْ وَجَبَ الْغُسْلُ . فَقَالَ أَبُو مُوسَى الأَشْعَرِيُّ لاَ أَسْأَلُ عَنْ هَذَا أَحَدًا بَعْدَكِ أَبَدًا .
Yahya related to me from Malik from Yahya ibn Said from Said ibn
al-Musayyab that Abu Musa al-Ashari came to A'isha, the wife of the
Prophet, may Allah bless him and grant him peace, and said to her,
"The disagreement of the companions in a matter which I hate to bring
before you has distressed me." She said, "What is that? You did not
ask your mother about it, so ask me." He said, "A man penetrates his
wife, but becomes listless and does not ejaculate. "She said, "When
the circumcised part passes the circumcised part ghusl is obligatory."
Abu Musa added, "I shall never ask anyone about this after you."
About Muwatta Malik
This hadith is #105 from Muwatta Malik, in the Book of Purity.