Abu Bishr (may Allah have mercy on him) said: I heard a man from the tribe of Banu Abd al-Dar say that a man came to Abdullah bin Amr (may Allah be pleased with him) and asked about a man in ihram who has intercourse with his wife, but he gave no answer. He went to Ibn Abbas (may Allah be pleased with him), and Abdullah bin Amr (may Allah be pleased with him) said: If anyone can tell him something about it, it is the cousin of the Messenger of Allah (peace and blessings be upon him). The narrator said: Ibn Abbas (may Allah be pleased with him) said: They should perform the remaining rites of Hajj, but perform Hajj again the following year; and when they come to the place where they committed the sin, they should separate there, and a sacrifice is due from each of the two of them; or he said: a sacrifice is due from both of them. Abu Bishr (may Allah have mercy on him) said: I mentioned this to Sa'id bin Jubayr (may Allah have mercy on him), and he said: That is how Ibn Abbas (may Allah be pleased with him) used to say it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9784