Bulugh al-Maram 141
Narrated `A'ishah (RAA):
Umm Habiba bint Jahsh complained to Allah's Messenger (Peace be upon him) about a prolonged flow of blood. He said to her, "Keep away (from prayer) as long as your normal period used to prevent you (from praying), and afterwards she should perform Ghusl (and pray)". (She used to take a bath for every prayer).
[Reported by Muslim.]
وَعَنْ عَائِشَةَ رَضِيَ اَللَّهُ عَنْهَا; { أَنَّ أُمَّ حَبِيبَةَ بِنْتَ جَحْشٍ شَكَتْ إِلَى رَسُولِ اَللَّهِ ‏- صلى الله عليه وسلم ‏-اَلدَّمَ, فَقَالَ: 
"اُمْكُثِي قَدْرَ مَا كَانَتْ تَحْبِسُكِ حَيْضَتُكِ, ثُمَّ اِغْتَسِلِي" فَكَانَتْ تَغْتَسِلُ كُلَّ صَلَاةٍ }  رَوَاهُ مُسْلِم ٌ  1‏ .‏‏1 ‏- صحيح.‏ رواه مسلم (334)‏ (66)‏.‏