Abu al-Ahwas narrates from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): When you catch one rak'ah of the Friday prayer, add another to it, and when you miss the bowing, pray four rak'ahs.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5739
Hadith Gradingمحدثین:صحيح لغيرهٖ
Hadith Takhrij«صحيح لغيرهٖ۔ أخرجه الشافعي في الام 7/296»