Sahih Muslim Book 8, Hadith Number 3449.

Chapter: How long after marrying one should stay with a virgin or a woman previously married.

Abu Qilaba reported on the authority of Anas: It is the Sunnah to stay with a virgin (after having married her) for a week. Khalid (one of the narrators) said: If wish I can say that it can be traced up to the Holy Prophet (May peace be upon him).