ʿUyūn akhbār al-Riḍā
Hadith 348348 - وَبِهذَا الإسناد قالَ: قالَ رَسُولَ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَآلِهِ: لا تفرد وَالجُمْعَةِ بصوم.
31-348 According to the same documentation, God’s Prophet (S) said, “Do not establish Friday as the only day of the week to fast.”