Muwatta Malik 346

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، عَنْ أَبِيهِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، كَانَ إِذَا قَدِمَ مَكَّةَ صَلَّى بِهِمْ رَكْعَتَيْنِ ثُمَّ يَقُولُ يَا أَهْلَ مَكَّةَ أَتِمُّوا صَلاَتَكُمْ فَإِنَّا قَوْمٌ سَفْرٌ ‏.‏

Yahya related to me from Malik from Ibn Shihab from Salim ibn Abdullah from his father that Umar ibn al-Khattab, when he went to Makka, used to lead them in prayer and do two rakas and then say, "People of Makka,complete the prayer, we are a group travelling

Reference

Muwatta Malik 346

In-book

Book 9, Hadith 21