مُوَطَّأُ مَالِكٍ
Muwatta Malik 352
Shortening the Prayer
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ صَفْوَانَ، أَنَّهُ قَالَ جَاءَ عَبْدُ اللَّهِ بْنُ عُمَرَ يَعُودُ عَبْدَ اللَّهِ بْنَ صَفْوَانَ فَصَلَّى لَنَا رَكْعَتَيْنِ ثُمَّ انْصَرَفَ فَقُمْنَا فَأَتْمَمْنَا .
Yahya related to me from Malik from Ibn Shihab that Safwan said, "Abdullah ibn Umar used to come and visit Abdullah ibn Safwan and he would pray two rakas with us, and when he went away we would stand and complete the prayer."
Arabic/English book reference: Book 9, Hadith 23