Talhah bin Abdullah bin Awf said: I offered the funeral prayer behind Sayyiduna Ibn Abbas (may Allah be pleased with them both), and I heard him reciting Surah al-Fatihah. When he finished, I asked him about it, and he said: "It is the Sunnah and it is the truth." In another narration, he did not mention 'the truth'.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6956