[Machine] I found this hadith in the book of my father. Hujjaj narrated to us from Shu'bah on the authority of Abu Ishaq, on the authority of Abu Safar, on the authority of Sa'id ibn Shu'ayb, on the authority of Ibn Abbas, that they used to ask him about praying while traveling. So Ibn Abbas said, "The Prophet ﷺ used to only pray two units (rak'ahs) when he left his family until he returned."  

وَجَدْتُ هَذَا الْحَدِيثَ فِي كِتَابِ أَبِي حَدَّثَنَا حَجَّاجٌ حَدَّثَنَا شُعْبَةُ عَنْ أَبِي إِسْحَاقَ عَنْ أَبِي السَّفَرِ عَنْ سَعِيدِ بْنِ شُفَيٍّ عَنِ ابْنِ عَبَّاسٍ أَنَّهُمْ جَعَلُوا يَسْأَلُونَهُ عَنِ الصَّلاةِ فِي السَّفَرِ؟ فَقَالَ ابْنُ عَبَّاسٍ كَانَ النَّبِيُّ ﷺ إِذَا خَرَجَ مِنْ أَهْلِهِ لَمْ يَزِدْ عَلَى رَكْعَتَيْنِ حَتَّى يَرْجِعَ