وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ سَالِمَ بْنَ عَبْدِ اللَّهِ، وَسُلَيْمَانَ بْنَ يَسَارٍ، سُئِلاَ عَنِ الْحَائِضِ، هَلْ يُصِيبُهَا زَوْجُهَا إِذَا رَأَتِ الطُّهْرَ قَبْلَ أَنْ تَغْتَسِلَ فَقَالاَ لاَ حَتَّى تَغْتَسِلَ ‏.‏

Yahya related to me from Malik that he had heard that Salim ibnAbdullah and Sulayman ibn Yasar were asked whether the husband of amenstruating woman could have sexual intercourse with her when she sawthat she was pure but before she had had a ghusl. They said, "No, notuntil she has had a ghusl." Translation Not Available

Book Ref: Muwatta Imam Malik Book 2 Hadith 128
Web Ref:  Muwatta Imam Malik Book 2 Hadith 98