Muwatta Malik, Book 20, Hadith 211 (USC-MSA) ⓘ

Yahya related to me from Malik from Ibn Shihab from Said ibn al- Musayyab that Umar ibn al-Khattab prayed two rakas with everybody when he arrived in Makka. Then, when he had finished, he said, "People of Makka, complete your prayer, because we are a group of travellers." Later, Umar ibn al-Khattab prayed two rakas with them at Mina, but we have not heard that he said anything to them on that occasion.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، ‏.‏ أَنَّ عُمَرَ بْنَ الْخَطَّابِ، لَمَّا قَدِمَ مَكَّةَ صَلَّى بِهِمْ رَكْعَتَيْنِ ثُمَّ انْصَرَفَ فَقَالَ يَا أَهْلَ مَكَّةَ أَتِمُّوا صَلاَتَكُمْ فَإِنَّا قَوْمٌ سَفْرٌ ‏.‏ ثُمَّ صَلَّى عُمَرُ بْنُ الْخَطَّابِ رَكْعَتَيْنِ بِمِنًى وَلَمْ يَبْلُغْنَا أَنَّهُ قَالَ لَهُمْ شَيْئًا ‏.‏