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."
Muwatta Malik Book 2, Hadith 97