If I wished, I could say, "The Messenger of Allah ﷺ said it," but he said, "It is the Sunnah that when a man marries a virgin while already having another wife, he stays with her for seven nights, and when he marries a previously married woman while already having another wife, he stays with her for three nights."
حدثنا أبو سلمة يحيى بن خلف حدثنا بشر بن المفضل عن خالد الحذاء عن أبي قلابة
لو شئت أن أقول قال رسول الله ﷺ ولكنه قال السنة إذا تزوج الرجل البكر على امرأته أقام عندها سبعا وإذا تزوج الثيب على امرأته أقام عندها ثلاثا
Agreed upon [by Bukhari and Muslim]. Bukhari narrated it in the Book of Nikah, chapter on justice among wives, "And you will never be able to..." [Nisa 4:129], no. 5213, from the hadith of Bishr, and Muslim narrated it, no. 1461, from the hadith of Khalid al-Hadhdha, through the same chain.There is also, on this subject, a report from Umm Salama [Muslim, no. 1460].