Mishkat al-Masabih 13 Marriage كتاب النكاح 215

وَعَنْ سُلَيْمَانَ بْنِ يَسَارٍ عَنْ سَلَمَةَ بْنِ صَخْرٍ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي الْمُظَاهِرِ يُوَاقِعُ قَبْلَ أَنْ يُكَفِّرَ قَالَ: «كَفَّارَة وَاحِدَة» . رَوَاهُ التِّرْمِذِيّ وَابْن مَاجَه

Sulaiman b. Yasar on the authority of Salama b. Sakhr, reported the Prophet as saying about one who vows to make his wife like his mother’s back and has intercourse with her before making atonement, “There is one atonement.”* * Atonement for breaking the vow should be made before doing so, but if the vow is broken then the same atonement is enough. Tirmidhi and Ibn Majah transmitted it.