Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates from Sayyidah Hafsah (may Allah be pleased with her), the wife of the Prophet (peace and blessings be upon him), that he (peace and blessings be upon him) said: "Attending the Friday prayer is obligatory on every adult, and ghusl is obligatory on whoever comes to the Friday prayer."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5653