Abbas bin al-Walid (may Allah have mercy on him) said: My father informed me that al-Awza'i (may Allah have mercy on him) was asked about a man who has intercourse with his wife in Ramadan. He said: There is a single expiation upon the two of them, except for the fasting, for the fasting is upon both of them. It was said to him: What if the woman was unwilling? He said: Then the fasting is upon the man alone.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8064