Sahih Bukhari
Wedlock, Marriage (Nikaah)
Volume: 007 / Book Number: 062 / Hadith Number: 4
Narrated '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."