It is disliked to single out Friday for fasting, unless it coincides with a day that one customarily fasts Sahih Muslim 1143 a
Translation
Muhammad b. 'Abbas b. Ja'far reported
I asked Jabir b. 'Abdullah (Allah be pleased with both of them) as he was circumambulating the House (Ka'ba) whether the Messenger of Allah (ﷺ) had forbidden the fasting on Friday, whereupon he said: Yes, by the Lord of this House.