كتاب الصيام
13  
The Book of Fasting
(24)
Chapter: It is disliked to single out Friday for fasting, unless it coincides with a day that one customarily fasts
(24)
باب كَرَاهِيَةِ صِيَامِ يَوْمِ الْجُمُعَةِ مُنْفَرِدًا
Sahih Muslim 1143 a

Muhammad b. 'Abbas b. Ja'far reported:

I asked Jabir b. 'Abdullah (Allah be pleased with both of them) as he was circumambulating the House (Ka'ba) whether the Messenger of Allah (ﷺ) had forbidden the fasting on Friday, whereupon he said: Yes, by the Lord of this House.
حَدَّثَنَا عَمْرٌو النَّاقِدُ، حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنْ عَبْدِ الْحَمِيدِ بْنِ جُبَيْرٍ، عَنْ مُحَمَّدِ، بْنِ عَبَّادِ بْنِ جَعْفَرٍ سَأَلْتُ جَابِرَ بْنَ عَبْدِ اللَّهِ - رضى الله عنهما - وَهُوَ يَطُوفُ بِالْبَيْتِ أَنَهَى رَسُولُ اللَّهِ صلى الله عليه وسلم عَنْ صِيَامِ يَوْمِ الْجُمُعَةِ فَقَالَ نَعَمْ وَرَبِّ هَذَا الْبَيْتِ ‏.‏
Reference : Sahih Muslim 1143a
In-book reference : Book 13, Hadith 187
USC-MSA web (English) reference : Book 6, Hadith 2543
  (deprecated numbering scheme)