I offered the prayer with the Prophet, Abu Bakr and ʿUmar at Mina and it was of two rakʿat. ʿUthman in the early days of his caliphate did the same, but later on he started praying the full prayer.  

صَلَّيْتُ مَعَ النَّبِيِّ ﷺ بِمِنًى رَكْعَتَيْنِ وَأَبِي بَكْرٍ وَعُمَرَ وَمَعَ عُثْمَانَ صَدْرًا مِنْ إِمَارَتِهِ ثُمَّ أَتَمَّهَا  

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  

His father said: "The Messenger of Allah ﷺ prayed two rak'ahs in Mina, and Abu Bakr prayed two rak'ahs, and Umar prayed two rak'ahs, and Uthman prayed (two rak'ahs) at the beginning of his Khilafah."  

صَلَّى رَسُولُ اللَّهِ ﷺ بِمِنًى رَكْعَتَيْنِ وَصَلاَّهَا أَبُو بَكْرٍ رَكْعَتَيْنِ وَصَلاَّهَا عُمَرُ رَكْعَتَيْنِ وَصَلاَّهَا عُثْمَانُ صَدْرًا مِنْ خِلاَفَتِهِ  

"I prayed two rak'ahs with the Messenger of Allah ﷺ in Mina, and with Abu Bakr and 'Umar, and two rak'ahs with 'Uthman at the beginning of his Caliphate." (Using translation from Nasāʾī 1447)   

صَلَّيْتُ مَعَ رَسُولِ اللهِ ﷺ بِمِنًى رَكْعَتَيْنِ وَمَعَ أَبِي بَكْرٍ رَكْعَتَيْنِ وَمَعَ عُمَرَ رَكْعَتَيْنِ وَمَعَ عُثْمَانَ صَدْرًا مِنْ خِلَافَتِهِ ثُمَّ صَلَّاهَا أَرْبَعًا  

I offered the prayer with the Prophet, Abu Bakr and ʿUmar at Mina and it was of two rakʿat. ʿUthman in the early days of his caliphate did the same, but later on he started praying the full prayer. (Using translation from Bukhārī 1082)  

صَلَّيْتُ مَعَ النَّبِيِّ ﷺ بِمِنًى رَكْعَتَيْنِ وَمَعَ أَبِي بَكْرٍ وَمَعَ عُمَرَ وَعُثْمَانَ صَدْرًا مِنْ إِمَارَتِهِ ثُمَّ أَتَمَّ  

[Machine] I prayed with the Prophet ﷺ in Mina two units of prayer, and with Abu Bakr, with Umar, and with Uthman, shoulder to shoulder, as part of his leadership, then I completed.  

صَلَّيْتُ مَعَ النَّبِيِّ ﷺ بِمِنًى رَكْعَتَيْنِ وَمَعَ أَبِي بَكْرٍ وَمَعَ عُمَرَ وَمَعَ عُثْمَانَ صَدْرًا مِنْ إِمَارَتِهِ ثُمَّ أَتَمَّ  

[Machine] It is narrated that the Prophet ﷺ , Abu Bakr, Umar, and Uthman prayed two units of prayer in Mina.  

أَنَّ النَّبِيَّ ﷺ وَأَبَا بَكْرٍ وَعُمَرَ وَعُثْمَانَ صَدْرًا مِنْ إِمَارَتِهِ صَلَّوْا بِمِنًى رَكْعَتَيْنِ  

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. (Using translation from Muslim 694a)  

«أَنَّ رَسُولَ اللَّهِ ﷺ صَلَّى صَلَاةَ الْمُسَافِرِ بِمِنًى رَكْعَتَيْنِ وَأَبُو بَكْرٍ وَعُمَرُ وَعُثْمَانُ رَكْعَتَيْنِ صَدْرًا مِنْ خِلَافَتِهِ ثُمَّ أَتَمَّهَا أَرْبَعًا»  

[Machine] The Messenger of Allah ﷺ performed two units of prayer and Abu Bakr, Umar, and Uthman shared the leadership with him.  

«صَلَّى رَسُولُ اللهِ ﷺ رَكْعَتَيْنِ وَأَبُو بَكْرٍ وَعُمَرُ وَعُثْمَانُ شَطْرًا مِنْ إِمَارَتِهِ»  

"I prayed two rak'ahs with the Messenger of Allah ﷺ in Mina, and with Abu Bakr and 'Umar, and two rak'ahs with 'Uthman at the beginning of his Caliphate." (Using translation from Nasāʾī 1447)   

صَلَّيْتُ مَعَ رَسُولِ اللهِ ﷺ بِمَكَّةَ وَبِمِنًى رَكْعَتَيْنِ وَمَعَ أَبِي بَكْرٍ رَكْعَتَيْنِ وَمَعَ عُمَرَ رَكْعَتَيْنِ وَمَعَ عُثْمَانَ صَدْرًا مِنْ خِلَافَتِهِ رَكْعَتَيْنِ  

His father said: "The Messenger of Allah ﷺ prayed two rak'ahs in Mina, and Abu Bakr prayed two rak'ahs, and Umar prayed two rak'ahs, and Uthman prayed (two rak'ahs) at the beginning of his Khilafah." (Using translation from Nasāʾī 1451)  

«صَلَّى رَسُولُ اللهِ ﷺ بِمِنًى رَكْعَتَيْنِ وَصَلَّاهَا أَبُو بَكْرٍ رَكْعَتَيْنِ وَصَلَّاهَا عُمَرُ رَكْعَتَيْنِ وَصَلَّاهَا عُثْمَانُ صَدْرًا مِنْ خِلَافَتِهِ رَكْعَتَيْنِ»