Hadith 8:121
A narration by Muslim has:
"Command him to take her back, then divorce her when she is pure from the menstrual discharge, or pregnant."
وَفِي رِوَايَةٍ لِمُسْلِمٍ : { مُرْهُ فَلْيُرَاجِعْهَا, ثُمَّ لْيُطَلِّقْهَا طَاهِرًا أَوْ حَامِلًا }