صَحِيحُ مُسْلِمٍ
Sahih Muslim 1143 a
The Book of Fasting
It is disliked to single out Friday for fasting, unless it coincides with a day that one customarily fasts
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 .
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.
Sahih Muslim, 1143 aSahihصحيح