Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: I was once with the Messenger of Allah (peace and blessings be upon him) when a man came and said: O Messenger of Allah! I am ruined, and I have caused ruin. He (peace and blessings be upon him) said: "Woe to you, what has happened to you?" He said: I had intercourse with my wife in Ramadan. He (peace and blessings be upon him) said: "Then free a slave." And he narrated the hadith in full.
(Our Shaykh Abu Abdullah al-Hafiz (may Allah have mercy on him) declared the words "and I have caused ruin" weak, and held that they were inserted into the narration of Muhammad bin al-Musayyab al-Arghiyani, since others narrated it from him and from al-Awza'i without these words, and none of al-Zuhri's students mentioned them except in what is narrated from Abu Thawr, from Mu'alla bin Mansur, from Sufyan bin Uyaynah, from al-Zuhri. Our Shaykh used to argue that these words are a mistake in that narration as well, because he looked in the Kitab al-Sawm compiled by Mu'alla bin Mansur, in a well-known handwriting, and found this hadith in it without these words, and all of Sufyan's students narrated it from him without them; and Allah knows best.)
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8063
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