"A man asked Abdullah bin Mas'ud about this phrase: 'Ghairi asin' or is it Yasin? So he said: 'You can recite all of the Quran besides this [phrase]?' He said: 'Yes.' He said: 'Indeed a people recite it, disbursing it like Ad-Daqqa are dispersed, without it passing their throats. Indeed I am aware of the surahs that are comparable which the Messenger of Allah would recite together.'" He said: "So we told Alqamah to ask him (what they were). He said: "Twenty surahs from the Mufassal from which the Prophet would combine, reciting every two Surah in a Rak'ah.'"
حَدَّثَنَا مَحْمُودُ بْنُ غَيْلاَنَ، حَدَّثَنَا أَبُو دَاوُدَ، قَالَ أَنْبَأَنَا شُعْبَةُ، عَنِ الأَعْمَشِ، قَالَ سَمِعْتُ أَبَا وَائِلٍ، قَالَ سَأَلَ رَجُلٌ عَبْدَ اللَّهِ عَنْ هَذَا الْحَرْفِ (غَيرِ آسِنٍ) أَوْ يَاسِنٍ قَالَ كُلَّ الْقُرْآنِ قَرَأْتَ غَيْرَ هَذَا الْحَرْفِ قَالَ نَعَمْ . قَالَ إِنَّ قَوْمًا يَقْرَءُونَهُ يَنْثُرُونَهُ نَثْرَ الدَّقَلِ لاَ يُجَاوِزُ تَرَاقِيَهُمْ إِنِّي لأَعْرِفُ السُّوَرَ النَّظَائِرَ الَّتِي كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَقْرِنُ بَيْنَهُنَّ . قَالَ فَأَمَرْنَا عَلْقَمَةَ فَسَأَلَهُ فَقَالَ عِشْرُونَ سُورَةً مِنَ الْمُفَصَّلِ كَانَ النَّبِيُّ صلى الله عليه وسلم يَقْرِنُ بَيْنَ كُلِّ سُورَتَيْنِ فِي رَكْعَةٍ . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ .
Tirmizi
The Book on Traveling • Hadith 601