Hadith 121

Bulugh al-Maram

Book 8: Marriage
وَفِي رِوَايَةٍ لِمُسْلِمٍ : { مُرْهُ فَلْيُرَاجِعْهَا, ثُمَّ لْيُطَلِّقْهَا طَاهِرًا أَوْ حَامِلًا } 1‏ .‏
A narration by Muslim has:

"Command him to take her back, then divorce her when she is pure from the menstrual discharge, or pregnant."