Sahih Al Bukhari Hadith Number 1984

Narrated Muhammad bin `Abbas: I asked Jabir “Did the Prophet (peace be upon him) forbid fasting on Fridays?” He replied, “Yes.” (Other narrators added, “If he intends to fast only that day.”)

30  Fasting
Hadith number 1984
Volume no 3
Chapter: 63 (Observing Saum (fast) on Friday)