Muslim bin Iyad said: I asked Sayyiduna Hasan bin Ali (may Allah be pleased with him) about the two rak'ahs of Jumu'ah, and he said: "These two (rak'ahs) suffice in place of what is besides them (the remaining rak'ahs of Zuhr)."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2676