Do not single out the night (preceding) Friday among the nights for prayer and do not single out Friday among days for fasting but only when anyone among you is accustomed to fast (on dates) which coincide with this day (Friday).  

عَنِ النَّبِيِّ ﷺ قَالَ لاَ تَخْتَصُّوا لَيْلَةَ الْجُمُعَةِ بِقِيَامٍ مِنْ بَيْنِ اللَّيَالِي وَلاَ تَخُصُّوا يَوْمَ الْجُمُعَةِ بِصِيَامٍ مِنْ بَيْنِ الأَيَّامِ إِلاَّ أَنْ يَكُونَ فِي صَوْمٍ يَصُومُهُ أَحَدُكُمْ  

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  

“While I was circumambulating the House, I asked Jabir bin ‘Abdullah: ‘Did the Prophet ﷺ forbid fasting on a Friday?’ He said: ‘Yes, by the Lord of this House.’”  

سَأَلْتُ جَابِرَ بْنَ عَبْدِ اللَّهِ وَأَنَا أَطُوفُ بِالْبَيْتِ أَنَهَى النَّبِيُّ ﷺ عَنْ صِيَامِ يَوْمِ الْجُمُعَةِ؟ قَالَ نَعَمْ وَرَبِّ هَذَا الْبَيْتِ  

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