Talhah bin Abdullah bin Awf (may Allah have mercy on him) said: I was behind Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) at a funeral, and he recited Surah al-Fatihah [Surah al-Fatihah: 1-7]. When he gave the salam, I asked him about it, and he said that it is the Sunnah and it is the truth. Ibrahim bin Hamzah narrated it from Ibrahim bin Sa'd and said that he recited Surah al-Fatihah [Surah al-Fatihah: 1-7] and also a (further) surah.
The mention of the surah in it is not preserved (ghayr mahfuz).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6954