Hadith: It is from the Sunnah that if someone marries a virgin, he should stay with her (the virgin) for seven days and then divide the nights between them. But if he marries a previously married woman, he should stay with her for three days, then divide the nights (between his wives)

عن أنس بن مالك رضي الله عنه قال: «من السنة إذا تَزَوَّجَ البِكْرَ على الثَّيِّبِ: أقام عندها سبعا ثم قَسَمَ. وإذا تَزَوَّجَ الثَّيِّبَ: أقام عندها ثلاثا ثم قَسَمَ». قال أبو قلابة:" ولو شِئْتُ لَقُلْتُ: إنَّ أَنَسًا رَفَعَهُ إلى النبي صلى الله عليه وسلم ».
[صحيح] - [متفق عليه]

Anas ibn Mālik (may Allah be pleased with him) reported: It is from the Sunnah that if someone marries a virgin, he should stay with her (the virgin) for seven days and then divide the nights between them. But if he marries a previously married woman, he should stay with her for three days, then divide the nights (between his wives). Abu Qilābah said: "If I wanted, I would say that Anas attributed this Hadīth directly to the Prophet (may Allah's peace and blessings be upon him)."
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

It is a directive from the Sunnah that when someone marries a virgin, he should stay with her for seven days to keep her company, and to remove her loneliness and also her shyness about the fact that she is recently married. He should then divide his time equally between his wives. If he marries a woman who was previously married, he should stay with her for three days, as her need is less than that of the virgin’s. This wise ruling is implied in this Hadīth reported directly from the Prophet (may Allah's peace and blessings be upon him) because when narrators say: "It is from the Sunnah," they can only mean the Prophet's Sunnah.