Ibn ‘Umar said that God’s Messenger prayed two <i>rak'as</i> in Mina, as did Abu Bakr after his death, ‘Umar after Abu Bakr’s death, and ‘Uthman in the early part of his Caliphate, but afterwards ‘Uthman prayed four. When Ibn ‘Umar prayed with an <i>imam</i> he prayed four, but when he prayed alone he prayed two. (Bukhari and Muslim.)

عَنِ ابْنِ عُمَرَ قَالَ: صَلَّى رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بمنى رَكْعَتَيْنِ وَأَبُو بَكْرٍ بَعْدَهُ وَعُمَرُ بَعْدَ أَبِي بَكْرٍ وَعُثْمَانُ صَدَرًا مِنْ خِلَافَتِهِ ثُمَّ إِنَّ عُثْمَانَ صَلَّى بَعْدُ أَرْبَعًا فَكَانَ ابْنُ عُمَرَ إِذَا صَلَّى مَعَ الْإِمَامِ صَلَّى أَرْبَعًا وَإِذَا صلاهَا وَحده صلى رَكْعَتَيْنِ