Language:
كتاب الوضوء
4
Ablutions (Wudu')
(64)
Chapter: The washing out of semen with water and rubbing it off (when it is dry) and the washing out of what comes out of women (i.e., discharge)
(64)
باب غَسْلِ الْمَنِيِّ وَفَرْكِهِ وَغَسْلِ مَا يُصِيبُ مِنَ الْمَرْأَةِ

Narrated `Aisha:

I used to wash the traces of Janaba (semen) from the clothes of the Prophet (ﷺ) and he used to go for prayers while traces of water were still on it (water spots were still visible).

حَدَّثَنَا عَبْدَانُ، قَالَ أَخْبَرَنَا عَبْدُ اللَّهِ، قَالَ أَخْبَرَنَا عَمْرُو بْنُ مَيْمُونٍ الْجَزَرِيُّ، عَنْ سُلَيْمَانَ بْنِ يَسَارٍ، عَنْ عَائِشَةَ، قَالَتْ كُنْتُ أَغْسِلُ الْجَنَابَةَ مِنْ ثَوْبِ النَّبِيِّ صلى الله عليه وسلم، فَيَخْرُجُ إِلَى الصَّلاَةِ، وَإِنَّ بُقَعَ الْمَاءِ فِي ثَوْبِهِ‏.‏
Reference : Sahih al-Bukhari 229
In-book reference : Book 4, Hadith 96
USC-MSA web (English) reference : Vol. 1, Book 4, Hadith 229
  (deprecated numbering scheme)