Musnad Ahmad 30:3079

Waki’ narrated to us, from Zam’ah—meaning Ibn Salih al-Makki—from al-Zuhri, from Sa’id ibn al-Musayyib, from Abu Hurairah: "That the Prophet, peace and blessings of Allah be upon him, prayed with his companions over al-Najashi, and he said the takbir four times."