[Machine] He used to pray four units (rak'ahs) when praying with the imam, and he used to pray two units (rak'ahs) when praying alone.  

أَنَّهُ كَانَ إِذَا صَلَّى مَعَ الْإِمَامِ صَلَّى أَرْبَعًا وَإِذَا صَلَّى وَحْدَهُ صَلَّى رَكْعَتَيْنِ  

[Machine] I asked Ibn Umar the traveler if he should pray two units of prayer with the residents or should he pray with their prayer? He laughed and said, "He should pray with their prayer."  

قُلْتُ لِابْنِ عُمَرَ الْمُسَافِرُ يُدْرِكُ رَكْعَتَيْنِ مِنْ صَلَاةِ الْقَوْمِ يَعْنِي الْمُقِيمِينَ أَتُجْزِيهُ الرَّكْعَتَانِ أَوْ يُصَلِّي بِصَلَاتِهِمْ؟ قَالَ فَضَحِكَ وَقَالَ يُصَلِّي بِصَلَاتِهِمْ