It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) offered a funeral prayer, said four takbirs over it, and gave a single salam. It is reported from Ata' bin al-Sa'ib (may Allah have mercy on him) as mursal that the Prophet (peace and blessings be upon him) offered the funeral prayer with a single salam to one side.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6982