Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: I never saw the Prophet (peace and blessings be upon him) fasting on a Friday.
Al-Tabarani recorded it in al-Mu'jam al-Kabir. Its chain contains Layth bin Abi Sulaym, who is thiqah (trustworthy) but a mudallis (one who conceals defects in the chain).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 5213