Sayyiduna Abdullah bin Abi Awfa (may Allah be pleased with him) said: I was present at a funeral, and he said four takbirs over the funeral. Then he paused for a while and supplicated, and said: "What do you think, did I intend to say five takbirs?" They said: "No." He said: "Indeed, the Messenger of Allah (peace and blessings be upon him) used to say four takbirs."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6937