Al Baqarah Ayah 226

لِّلَّذِينَ يُؤْلُونَ مِن نِّسَآئِهِمْ تَرَبُّصُ أَرْبَعَةِ أَشْهُرٍ‌ۖ فَإِن فَآءُو فَإِنَّ ٱللَّهَ غَفُورٌ رَّحِيمٌ ٢٢٦ Those who swear not to have intercourse with their wives must wait for four months. If they change their mind, then Allah is certainly All-Forgiving, Most Merciful.