Sahih Bukhari Volume 007, Book 062, Hadith Number 004.
Narrated By 'Abdullah : We were with the Prophet while we were young and had no wealth whatever. So Allah's Apostle said, "O young people! Whoever among you can marry, should marry, because it helps him lower his gaze and guard his modesty (i.e. his private parts from committing illegal sexual intercourse etc.), and whoever is not able to marry, should fast, as fasting diminishes his sexual power."