When the Messenger of Allah ﷺ married Umm Salama, he stayed with her for three nights and said, "You are not held in low regard by your husband. If you wish, I will spend seven nights with you, but if I spend seven with you, I will spend seven with each of my other wives."
أن رسول الله ﷺ لما تزوج أم سلمة أقام عندها ثلاثا وقال: إنه ليس بك على أهلك هوان، إن شئت سبعت لك، وإن سبعت لك سبعت لنسائي.
Muslim narrated it in the Book of Suckling (41:1460) via Yahya bin Saeed (that is, Ibn Qattan), from Sufyan (that is, Thawri), from Muhammad bin Abu Bakr, from Abdul-Malik bin Abu Bakr bin Abdul-Rahman bin Harith bin Hisham, from his father, from Umm Salama. However, Bukhari in his Tarikh al-Kabir (1/47) holds that Sufyan Thawri was not corroborated in his statement, "He stayed with her three days." And he is correct in this, for Muslim, following the hadith of Sufyan, narrated from the hadith of Malik, from Abdullah bin Abu Bakr, from Abdul-Malik bin Abu Bakr bin Abdul-Rahman, that when the Messenger of Allah ﷺ married Umm Salama and she came to live with him, he said to her, "You are not lowly in the eyes of your family. If you wish, I will stay with you seven days, and if you wish, three days, then continue with my rounds." She said, "Three."He also narrated it through another route, from Abu Bakr bin Abdul-Rahman, that when the Messenger of Allah ﷺ married Umm Salama, he went in to her, then intended to leave, but she took hold of his garment, so the Messenger of Allah ﷺ said, "If you wish, I will give you more and reckon it against you, for the virgin it is seven days, and for the previously married it is three days." He then connected the narration mentioning Umm Salama, and in it, "If you wish, I will stay seven days with you, and seven with my other wives, and if I stay seven with you, I will stay seven with my other wives."In these narrations there is an indication that he ﷺ gave her the choice after the first day, and she chose three, not that he stayed with her three days and then gave her the choice of extending it to seven, as Sufyan said. In this there is evidence for the majority view that it is from the sunnah for him to stay with the virgin seven days, and with the previously married woman three days, contrary to Abu Hanifa and his companions, who say that no wife is singled out for this, but rather he must make up the same for the rest of his wives, holding to the general principle of equal treatment among them. Perhaps this hadith did not reach them, for it is a specific exception to that general rule of equal treatment.If it is asked, if the virgin gets seven days and the previously married woman gets three, why then did he give her the choice between seven and three?The answer is, had she chosen seven, he would have owed seven days to the rest of his wives, and her right to the three days would have lapsed. For this reason she chose three, so that her right to the three days would not be lost, since the three days do not require making up an equivalent for the other wives, unlike the seven days, which would require making up the same for the rest of the wives.