Sunan an-Nasa'i 1988
It was narrated that Talhah bin 'Abdullah said:
"I offered the funeral prayer behind Ibn 'Abbas and I heard him reciting Fatihat Al-Kitab. When he finished I took him by the hand and asked him. 'Did you recite?' He said: 'Yes, it is the truth and the Sunnah."'
أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا مُحَمَّدٌ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ سَعْدِ بْنِ إِبْرَاهِيمَ، عَنْ طَلْحَةَ بْنِ عَبْدِ اللَّهِ، قَالَ صَلَّيْتُ خَلْفَ ابْنِ عَبَّاسٍ عَلَى جَنَازَةٍ فَسَمِعْتُهُ يَقْرَأُ، بِفَاتِحَةِ الْكِتَابِ فَلَمَّا انْصَرَفَ أَخَذْتُ بِيَدِهِ فَسَأَلْتُهُ فَقُلْتُ تَقْرَأُ قَالَ نَعَمْ إِنَّهُ حَقٌّ وَسُنَّةٌ ‏.‏