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.  

غَزَوْتُ مَعَ رَسُولِ اللَّهِ ﷺ وَشَهِدْتُ مَعَهُ الْفَتْحَ فَأَقَامَ بِمَكَّةَ ثَمَانِيَ عَشْرَةَ لَيْلَةً لاَ يُصَلِّي إِلاَّ رَكْعَتَيْنِ وَيَقُولُ يَا أَهْلَ الْبَلَدِ صَلُّوا أَرْبَعًا فَإِنَّا قَوْمٌ سَفْرٌ  

[Machine] When the Messenger of Allah ﷺ opened Mecca, he stayed there for eighteen nights, performing two raka'ahs (units of prayer) except for Maghrib prayer. Then he would say, "O people of Mecca, complete your prayers, for we are a traveling people."  

لَمَّا فَتْحَ رَسُولُ اللهِ ﷺ مَكَّةَ أَقَامَ بِهَا ثَمَانِ عَشْرَةَ لَيْلَةً يُصَلِّي بِأَهْلِ مَكَّةَ رَكْعَتَيْنِ إِلَّا الْمَغْرِبَ ثُمَّ يَقُولُ «يَا أَهْلَ مَكَّةَ أَتِمُّوا صَلَاتَكُمْ فَإِنَّا قَوْمٌ سَفْرٌ»  

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  

"أقَمْتُ مَعَ النَّبِىِّ ﷺ عَامَ الْفَتْحِ بِمَكَّةَ فَأَقَامَ ثَمانِ عَشْرَةَ لَا يُصَلِّى رَكْعَتَيْنِ ثُمَّ يَقُولُ لإهْلِ البَلَد صَلُّوا أَرْبَعًا فَإِنَّا قَوْمٌ سَفرٌ".