I went on an expedition with the Messenger of Allah ﷺ, and I was present with him at the conquest. He stayed eighteen days in Mecca and prayed only two rak'ahs (at each time of prayer). And he said: You who live in the town must pray four; we are travellers. (Using translation from Abū Dāʾūd 1229)   

غَزَوْتُ مَعَ النَّبِيِّ ﷺ وَشَهِدْتُ مَعَهُ الْفَتْحَ فَأَقَامَ بِمَكَّةَ ثَمَانِ عَشْرَةَ لَيْلَةً لَا يُصَلِّي إِلَّا رَكْعَتَيْنِ يَقُولُ يَا أَهْلَ الْبَلَدِ صَلُّوا أَرْبَعًا فَإِنَّا سَفْرٌ وَرُوِّينَا قَبْلَ هَذَا فِي الْحَدِيثِ عَنْ أَبِي بَكْرٍ وَعُمَرَ مِثْلُ ذَلِكَ  

[Machine] After he has delivered the greeting, complete the prayer, oh people of Makkah; for we are traveling.  

لَهُمْ بَعْدَمَا سَلَّمَ أَتِمُّوا الصَّلَاةَ يَا أَهْلَ مَكَّةَ؛ فَإِنَّا سَفْرٌ  

[Machine] That he said: Abdullah bin Umar came and Abdullah bin Safwan performed two raka'ahs (units of prayer) for us, then left, so we stood up and completed.  

أَنَّهُ قَالَ جَاءَ عَبْدُ اللهِ بْنُ عُمَرَ يَعُودُ عَبْدَ اللهِ بْنَ صَفْوَانَ فَصَلَّى لَنَا رَكْعَتَيْنِ ثُمَّ انْصَرَفَ فَقُمْنَا فَأَتْمَمْنَا