أَخْبَرَنَا يَزِيدُ بْنُ هَارُونَ، عَنْ هِشَامٍ، عَنْ الْحَسَنِ فِي الرَّجُلِ يَطَأُ امْرَأَتَهُ وَقَدْ رَأَتْ الطُّهْرَ قَبْلَ أَنْ تَغْتَسِلَ، قَالَ: "هِيَ حَائِضٌ مَا لَمْ تَغْتَسِلْ، وَعَلَيْهِ الْكَفَّارَةُ، وَلَهُ أَنْ يُرَاجِعَهَا مَا لَمْ تَغْتَسِلْ".
It is narrated from Imam Hasan, may Allah have mercy on him, about the man who has intercourse with his wife after her period but before she has performed ghusl (ritual bath), he said: Until she performs ghusl, she is under the same ruling as a menstruating woman, and expiation is due upon him. He should ask about the matter of ghusl.