Sahih al-Bukhari 5213
Narrated Anas:
The tradition, (of the Prophet) is that if someone marries a virgin and he has already a matron wife 
(with him), then he should stay with the virgin for seven days; and if someone marries a matron (and 
he has already a virgin wife with him) then he should stay with her for three days.
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا بِشْرٌ، حَدَّثَنَا خَالِدٌ، عَنْ أَبِي قِلاَبَةَ، عَنْ أَنَسٍ ـ رضى الله عنه ـ وَلَوْ شِئْتُ أَنْ أَقُولَ قَالَ النَّبِيُّ صلى الله عليه وسلم وَلَكِنْ قَالَ السُّنَّةُ إِذَا تَزَوَّجَ الْبِكْرَ أَقَامَ عِنْدَهَا سَبْعًا، وَإِذَا تَزَوَّجَ الثَّيِّبَ أَقَامَ عِنْدَهَا ثَلاَثًا‏.‏