I heard the Prophet (ﷺ) saying, "None of you should fast on Friday unless he fasts a day before or after it."
Sahih al-Bukhari Book 30, Hadith 92
← Previous Hadith 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.")

Sahih al-Bukhari Book 30, Hadith 91 Next Hadith → The Prophet (ﷺ) visited her (Juwairiya) on a Friday and she was fasting. He asked her, "Did you fast yesterday?" She said, "No." He said, "Do you intend to fast tomorrow?" She said, "No." He said, "Then break your fast." Through another series of narrators, Abu Aiyub is reported to have said, "He ordered her and she broke her fast."

Sahih al-Bukhari Book 30, Hadith 93