Reference: Fataawa Ramadhaan – Volume 2, Page 662, Fatwa No.668
Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa. – Fatwa No.8966
Question: If a person had one fast from Ramadhaan to make up, is it permissible for him to fast on a Friday?
Response: It is permissible for a Muslim to fast on a Friday if he is making up a fast from Ramadhaan, even if it is just one day.
And with Allaah lies all the success, and may Allaah send prayers and salutations upon our Prophet Muhammad (sal-Allaahu ‘alayhi wa sallam) and his family and his companions.