Abu Umamah bin Sahl (may Allah be pleased with him) said that one of the Companions (may Allah be pleased with him) of the Prophet (peace and blessings be upon him) informed him: "The Sunnah in the funeral prayer is that the imam says takbir, then after the first takbir recites Surah al-Fatihah silently to himself, then sends blessings upon the Prophet (peace and blessings be upon him), and in the takbirs makes sincere supplication for the deceased without reciting anything, then gives the salam silently to himself."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6959