Hadith 2540
Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) dispatched an army consisting of a few individuals. The Messenger of Allah (peace and blessings be upon him) called them and asked: "How much of the Qur'an have you memorized?" He then had each of them recite the Qur'an in turn. When it was the turn of one young man among them, the Prophet (peace and blessings be upon him) asked: "O young man, how much of the Qur'an have you memorized?" He replied that he had memorized such and such amount of the Qur'an and also Surah Al-Baqarah. The Prophet (peace and blessings be upon him) said: "Go, you are their leader."
Hadith 2541
Sayyiduna Umar (may Allah be pleased with him) said that when there is a group of three people, they should appoint one of them as their leader. The Messenger of Allah (peace and blessings be upon him) used to appoint leaders for people in this manner.