The Messenger of Allah ﷺ forbade fasting on Friday unless it is accompanied by a day of fasting before it or after it.
حدثنا أبو بكر بن أبي شيبة حدثنا أبو معاوية وحفص بن غياث عن الأعمش عن أبي صالح
نهى رسول الله ﷺ عن صوم يوم الجمعة إلا بيوم قبله أو يوم بعده
Bukhari, Fasting, chapter "The Fast of Friday, etc.," no. 1985, from the hadith of Amash, with this wording. Also Muslim, Fasting, chapter on the dislike of singling out Friday for fasting when it does not coincide with one's usual practice, no. 1144, from Abu Bakr bin Abu Shayba and others.