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