Salim b. 'Abdullah (b. 'Umar) reported on the authority of his father that Messenger of Allah ﷺ observed the prayer of a traveller, i. e. two rak'ahs in Mina, and other places; so did Abu Bakr and 'Umar, and 'Uthman too observed two rak'ahs at the beginning of his caliphate, but he then completed four.  

عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ صَلَّى صَلاَةَ الْمُسَافِرِ بِمِنًى وَغَيْرِهِ رَكْعَتَيْنِ وَأَبُو بَكْرٍ وَعُمَرُ وَعُثْمَانُ رَكْعَتَيْنِ صَدْرًا مِنْ خِلاَفَتِهِ ثُمَّ أَتَمَّهَا أَرْبَعًا  

A hadith like this has been reported by Zuhri, with the same chain of transmitters, and in it mention was made of Mina only, but not of other places.  

بِمِنًى وَلَمْ يَقُلْ وَغَيْرِهِ  

The Messenger of Allah ﷺ said two rak'ahs at Mina, and Abu Bakr after him, and 'Umar after Abu Bakr, and 'Uthman at the beginning of his caliphate; then 'Uthman observed four rak'ahs, and when Ibn 'Umar prayed with the Imam, he said four rak'ahs, but when he observed prayer alone, he said two rak'ahs.  

صَلَّى رَسُولُ اللَّهِ ﷺ بِمِنًى رَكْعَتَيْنِ وَأَبُو بَكْرٍ بَعْدَهُ وَعُمَرُ بَعْدَ أَبِي بَكْرٍ وَعُثْمَانُ صَدْرًا مِنْ خِلاَفَتِهِ ثُمَّ إِنَّ عُثْمَانَ صَلَّى بَعْدُ أَرْبَعًا فَكَانَ ابْنُ عُمَرَ إِذَا صَلَّى مَعَ الإِمَامِ صَلَّى أَرْبَعًا وَإِذَا صَلاَّهَا وَحْدَهُ صَلَّى رَكْعَتَيْنِ  

A hadith like this has been narrated by the same chain of transmitters.  

عَنْ عُبَيْدِ اللَّهِ بِهَذَا الإِسْنَادِ نَحْوَهُ  

The Apostle of Allah ﷺ said in Mina the prayer of a traveller (short prayer) ; Abu Bakr and 'Umar did the same and 'Uthmia did it for eight years or six years. Hafs (one of the narrators) said: Ibn 'Umar would also say two rak'ahs at Mina and then go to bed. I said to him: O uncle, I wish you could have said two rak'ahs (of Sunnah prayer after shorenting the Fard prayer). He said: Were I to do that, I would have completed the prayer.  

صَلَّى النَّبِيُّ ﷺ بِمِنًى صَلاَةَ الْمُسَافِرِ وَأَبُو بَكْرٍ وَعُمَرُ وَعُثْمَانُ ثَمَانِيَ سِنِينَ أَوْ قَالَ سِتَّ سِنِينَ قَالَ حَفْصٌ وَكَانَ ابْنُ عُمَرَ يُصَلِّي بِمِنًى رَكْعَتَيْنِ ثُمَّ يَأْتِي فِرَاشَهُ فَقُلْتُ أَىْ عَمِّ لَوْ صَلَّيْتَ بَعْدَهَا رَكْعَتَيْنِ قَالَ لَوْ فَعَلْتُ لأَتْمَمْتُ الصَّلاَةَ  

He prayed while travelling.  

حَدَّثَنَا شُعْبَةُ بِهَذَا الإِسْنَادِ وَلَمْ يَقُولاَ فِي الْحَدِيثِ بِمِنًى وَلَكِنْ قَالاَ صَلَّى فِي السَّفَرِ  

I heard 'Abd al-Rahman as saying; 'Uthman led us four rak'ahs of prayer at Mina. It was reported to Abdullah b. Mas'ud and he recited:" Surely we are Allah's and to Him shall we return," and then said: I prayed with the Messenger of Allah ﷺ at Mina two rak'ahs of prayer. I prayed along with Abu Bakr al-Siddiq two rak'ahs of prayer at Mina. I prayed along with 'Umar b. Khattab two rak'ahs of prayer at Mina. I wish I had my share of the two rak'ahs acceptable (to God) for the four rak'ahs.  

صَلَّيْتُ مَعَ رَسُولِ اللَّهِ ﷺ بِمِنًى رَكْعَتَيْنِ وَصَلَّيْتُ مَعَ أَبِي بَكْرٍ الصِّدِّيقِ بِمِنًى رَكْعَتَيْنِ وَصَلَّيْتُ مَعَ عُمَرَ بْنِ الْخَطَّابِ بِمِنًى رَكْعَتَيْنِ فَلَيْتَ حَظِّي مِنْ أَرْبَعِ رَكَعَاتٍ رَكْعَتَانِ مُتَقَبَّلَتَانِ  

A hadith like this has been reported by A'mash with the same chain of transmitters.  

عَنِ الأَعْمَشِ بِهَذَا الإِسْنَادِ نَحْوَهُ  

I prayed with the Messenger of Allah ﷺ two rak'ahs and most of them offered two rak'ahs only in Mina, while the people felt secure.  

صَلَّيْتُ مَعَ رَسُولِ اللَّهِ ﷺ بِمِنًى آمَنَ مَا كَانَ النَّاسُ وَأَكْثَرَهُ رَكْعَتَيْنِ  

I prayed behind the Messenger of Allah ﷺ at Mina, and there was the greatest number of people, and they prayed two rak'ahs on the occasion of the Farewell Pilgrimage. (Muslim said: Haritha b. Wahb al-Khuza'i is the brother of 'Ubaidullah b. 'Umar son of Khattab from the side of his mother.)  

صَلَّيْتُ خَلْفَ رَسُولِ اللَّهِ ﷺ بِمِنًى وَالنَّاسُ أَكْثَرُ مَا كَانُوا فَصَلَّى رَكْعَتَيْنِ فِي حَجَّةِ الْوَدَاعِ قَالَ مُسْلِمٌ حَارِثَةُ بْنُ وَهْبٍ الْخُزَاعِيُّ هُوَ أَخُو عُبَيْدِ اللَّهِ بْنِ عُمَرَ بْنِ الْخَطَّابِ لأُمِّهِ