It is the Prophet's tradition that if someone marries a virgin and he has already a matron wife then he should stay for seven days with her (the virgin) and then by turns; and if someone marries a matron and he has already a virgin wife then he should stay with her (the matron) for three days, and then by turns.  

مِنَ السُّنَّةِ إِذَا تَزَوَّجَ الرَّجُلُ الْبِكْرَ عَلَى الثَّيِّبِ أَقَامَ عِنْدَهَا سَبْعًا وَقَسَمَ وَإِذَا تَزَوَّجَ الثَّيِّبَ عَلَى الْبِكْرِ أَقَامَ عِنْدَهَا ثَلاَثًا ثُمَّ قَسَمَ قَالَ أَبُو قِلاَبَةَ وَلَوْ شِئْتُ لَقُلْتُ إِنَّ أَنَسًا رَفَعَهُ إِلَى النَّبِيِّ ﷺ وَقَالَ عَبْدُ الرَّزَّاقِ أَخْبَرَنَا سُفْيَانُ عَنْ أَيُّوبَ وَخَالِدٍ قَالَ خَالِدٌ وَلَوْ شِئْتُ قُلْتُ رَفَعَهُ إِلَى النَّبِيِّ ﷺ  

[Machine] If a virgin woman marries a previously married man, he must pay her seven days' worth of expenses. But if a previously married man marries a virgin woman, he must pay her three days' worth of expenses. Even if you say he raised the amount, you would be correct, but he said it is the sunnah (tradition) like this.  

إِذَا تَزَوَّجَ الْبِكْرَ عَلَى الثَّيِّبِ أَقَامَ عِنْدَهَا سَبْعًا وَإِذَا تَزَوَّجَ الثَّيِّبَ عَلَى الْبِكْرِ أَقَامَ عِنْدَهَا ثَلَاثًا وَلَوْ قُلْتَ إِنَّهُ رَفَعَهُ صَدَقْتَ وَلَكِنَّهُ قَالَ السُّنَّةُ كَذَلِكَ