Musnad Ahmad 482:117

Abu Abd al-Rahman narrated to us, Musa ibn Ali narrated to us, he said: I heard my father say: I heard Uqbah ibn Amir al-Juhani say: The Messenger of Allah (peace and blessings of Allah be upon him) came out to us one day while we were in the Suffah, and he said: "Which of you would like to go out every morning to Buthan or al-Aqiq, and bring back two large-humped, fat she-camels every day, without committing a sin or severing ties of kinship?" We said: "O Messenger of Allah, all of us would like that." He said: "For one of you to go out to the mosque and learn two verses from the Book of Allah is better for him than two she-camels, and three is better than three, and four is better than four, and [so on] according to their numbers in camels."