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  

The Prophet ﷺ led us in a two-rakʿat prayer at Mina although our number was more than ever and we were in better security than ever.  

صَلَّى بِنَا النَّبِيُّ ﷺ وَنَحْنُ أَكْثَرُ مَا كُنَّا قَطُّ وَآمَنُهُ بِمِنًى رَكْعَتَيْنِ