Musnad Abu Ya'la al-Mawsili 155:148

Khalid ibn Mirdas narrated to us, Abdullah ibn al-Mubarak narrated to us, from Ma'mar, Yunus, Malik, and al-Awza'i, from al-Zuhri, from Abu Salamah, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever catches a rak'ah of the prayer, he has caught it." Ma'mar said: Al-Zuhri said: "So we consider Jumu'ah to be of the prayer."