Muwatta Malik, Book 2, Hadith 98 (USC-MSA) ⓘ

Yahya related to me from Malik that he had heard that Salim ibn Abdullah and Sulayman ibn Yasar were asked whether the husband of a menstruating woman could have sexual intercourse with her when she saw that she was pure but before she had had a ghusl. They said, "No, not until she has had a ghusl."

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 ‏.‏