Yahya bin Abi Kathir يحيى بن أبي كثير الطائي · The Book on Jana''iz (Funerals)

"The Prophet prayed and in the funeral prayer he for An-Najashi, said four Takbir."

"I accompanied Abu Hurairah for ten years, and I heard him saying: 'I heard the Messenger of Allah saying: "Whoever follows a funeral, and carries it three times, then he has fulfilled the right that is required from him."