Sa'id bin Abi Sa'id said: I heard Ibn Abbas (may Allah be pleased with them both) reciting Surah al-Fatihah aloud (in a funeral prayer), and he said: "I have only done this so that you may know that it is the Sunnah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6957