When anyone who has already a wife marries virgin, he should stay with her for seven nights (and then turn to his other wife), but when anyone having a virgin with him (as his wife) marries a woman who has been previously married he should stay with her for three nights. Khalid (one of the narrators) said. If I were to say that it could be directly traced to the Prophet ﷺ. I would have told the truth, but he (Hadrat Anas) said: Such is the tradition.  

إِذَا تَزَوَّجَ الْبِكْرَ عَلَى الثَّيِّبِ أَقَامَ عِنْدَهَا سَبْعًا وَإِذَا تَزَوَّجَ الثَّيِّبَ عَلَى الْبِكْرِ أَقَامَ عِنْدَهَا ثَلاَثًا قَالَ خَالِدٌ وَلَوْ قُلْتُ إِنَّهُ رَفَعَهُ لَصَدَقْتُ وَلَكِنَّهُ قَالَ السُّنَّةُ كَذَلِكَ  

When a man who has a wife married a virgin he should stay with her seven nights ; if he marries to a woman who has been previously married he should stay with her three nights. (The narrator said:) If I say that he (Anas) narrated this tradition from the Prophet ﷺ I shall be true. But he said: The Sunnah is so-and-so.  

إِذَا تَزَوَّجَ الْبِكْرَ عَلَى الثَّيِّبِ أَقَامَ عِنْدَهَا سَبْعًا وَإِذَا تَزَوَّجَ الثَّيِّبَ أَقَامَ عِنْدَهَا ثَلاَثًا وَلَوْ قُلْتُ إِنَّهُ رَفَعَهُ لَصَدَقْتُ وَلَكِنَّهُ قَالَ السُّنَّةُ كَذَلِكَ  

[Machine] From the Sunnah, if a virgin marries a non-virgin, he should stay with her for seven nights. And if a non-virgin marries a virgin, he should stay with her for three nights. Khalid said, "If you say that he raised it, then you are truthful," and in a hadith from Abdul Razzaq, "If you want, you can say that he raised it to the Prophet ﷺ ."  

مِنَ السُّنَّةِ إِذَا تَزَوَّجَ الْبِكْرَ عَلَى الثَّيِّبِ أَقَامَ عِنْدَهَا سَبْعًا وَإِذَا تَزَوَّجَ الثَّيِّبَ عَلَى الْبِكْرِ أَقَامَ عِنْدَهَا ثَلَاثًا قَالَ خَالِدٌ وَلَوْ قُلْتَ إِنَّهُ رَفَعَهُ لَصَدَقْتَ وَفِي حَدِيثِ عَبْدِ الرَّزَّاقِ وَلَوْ شِئْتَ قُلْتَ رَفَعَهُ إِلَى النَّبِيِّ ﷺ