Yahya related to me from Malik from Ibn Shihab from Salim ibn Abdullah that Abdullah ibn Umar used to say, "I pray the prayerof a traveller as long as I am undecided whether to remain somewhere or not, even if I am detained for twelve nights."  

أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ كَانَ يَقُولُ أُصَلِّي صَلاَةَ الْمُسَافِرِ مَا لَمْ أُجْمِعْ مُكْثًا وَإِنْ حَبَسَنِي ذَلِكَ اثْنَتَىْ عَشْرَةَ لَيْلَةً  

Yahya related to me from Malik from Nafi that Ibn Umar stayed in Makka for ten nights, shortening the prayer, except when he prayed it behind an imam, in which case he followed the imam's prayer.  

أَنْ يُصَلِّيَهَا مَعَ الإِمَامِ فَيُصَلِّيهَا بِصَلاَتِهِ