Mukhtasar Bukhari

Narrated Abdullah bin Umar (may Allah be pleased with them): I offered two rak'ahs of prayer in Mina along with the Prophet (peace be upon him), Abu Bakr (may Allah be pleased with him), and Umar (may Allah be pleased with him), and also with the Commander of the Faithful, Uthman (may Allah be pleased with him), during the early period of his caliphate (I also prayed two rak'ahs). After that, he started offering the full prayer.

Haritha bin Wahb (may Allah be pleased with him) narrates that the Prophet Muhammad (peace be upon him) led us in a two-unit prayer at Mina during a time of complete peace.

Narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): When it was said to him that Ameer-ul-Mu'mineen Uthman bin Affan (may Allah be pleased with him) led us in four rak'ahs of prayer at Mina, he said, "Inna lillahi wa inna ilayhi raji'un." Then he said, "I performed two rak'ahs at Mina with the Messenger of Allah (peace and blessings of Allah be upon him), and I performed two rak'ahs at Mina with Ameer-ul-Mu'mineen Sayyiduna Abu Bakr Siddiq (may Allah be pleased with him), and I performed two rak'ahs at Mina with Ameer-ul-Mu'mineen Umar bin Khattab (may Allah be pleased with him). Would that, instead of these four rak'ahs, I had those two accepted rak'ahs (which the Noble Prophet (peace and blessings of Allah be upon him) and Ameer-ul-Mu'mineen Abu Bakr and Umar (may Allah be pleased with them both) used to perform)."