Sahih Bukhari Volume 007, Book 062, Hadith Number 003.
Narrated By 'Alqama : While I was with Abdullah, 'Uthman met him at Mina and said, "O Abu 'Abdur-Rahman ! I have something to say to you." So both of them went aside and 'Uthman said, "O Abu 'Abdur-Rah. man! Shall we marry you to a virgin who will make you remember your past days?" When 'Abdullah felt that he was not in need of that, he beckoned me (to join him) saying, "O 'Alqama!" Then I heard him saying (in reply to 'Uthman), "As you have said that, (I tell you that) the Prophet once said to us, 'O young people! Whoever among you is able to marry, should marry, and whoever is not able to marry, is recommended to fast, as fasting diminishes his sexual power.