Ibn Abi Layla says that Sayyiduna Zayd bin Arqam (may Allah be pleased with him) used to say four takbirs over our funerals. On one funeral, he said five takbirs. When people asked him about it, he said: "The Messenger of Allah (peace and blessings be upon him) also used to say five takbirs," or he said: "The Noble Prophet (peace and blessings be upon him) also said five takbirs."