(63) بَابُ صَوْمِ يَوْمِ الْجُمُعَةِ، فَإِذَا أَصْبَحَ صَائِمًا يَوْمَ الْجُمُعَةِ فَعَلَيْهِ أَنْ يُفْطِرَ
Narrated Muhammad bin `Abbas:
I asked Jabir "Did the Prophet (ﷺ) forbid fasting on Fridays?" He replied, "Yes." (Other narrators added, "If he intends to fast only that day.")
Reference: Sahih al-Bukhari 1984
In-book reference: Book 30, Hadith 91
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 31, Hadith 205