Humayd al-Fazari narrates from a woman of his tribe that Sayyiduna Ibn Mas'ud (may Allah be pleased with him) came to us on a Friday and asked: How do you pray? Then he said: When you pray with the imam, pray as he prays; and when you pray on your own, then pray four rak'ahs.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5650