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.")  

سَأَلْتُ جَابِرًا ؓ نَهَى النَّبِيُّ ﷺ عَنْ صَوْمِ يَوْمِ الْجُمُعَةِ قَالَ نَعَمْ زَادَ غَيْرُ أَبِي عَاصِمٍ أَنْ يَنْفَرِدَ بِصَوْمٍ  

I heard the Prophet ﷺ saying, "None of you should fast on Friday unless he fasts a day before or after it."  

سَمِعْتُ النَّبِيَّ ﷺ يَقُولُ لاَ يَصُومَنَّ أَحَدُكُمْ يَوْمَ الْجُمُعَةِ إِلاَّ يَوْمًا قَبْلَهُ أَوْ بَعْدَهُ  

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."  

عَنْ جُوَيْرِيَةَ بِنْتِ الْحَارِثِ ؓ أَنَّ النَّبِيَّ ﷺ دَخَلَ عَلَيْهَا يَوْمَ الْجُمُعَةِ وَهْىَ صَائِمَةٌ فَقَالَ أَصُمْتِ أَمْسِ قَالَتْ لاَ قَالَ تُرِيدِينَ أَنْ تَصُومِي غَدًا قَالَتْ لاَ قَالَ فَأَفْطِرِي وَقَالَ حَمَّادُ بْنُ الْجَعْدِ سَمِعَ قَتَادَةَ حَدَّثَنِي أَبُو أَيُّوبَ أَنَّ جُوَيْرِيَةَ حَدَّثَتْهُ فَأَمَرَهَا فَأَفْطَرَتْ