Musnad Imam Shafi'i

It is narrated from Ibn Abbas (may Allah be pleased with him) that a man came to the Messenger of Allah (peace and blessings be upon him) and said, "O Messenger of Allah! By Allah, since the date palms were grafted, I have not been with my family." Ibn Abbas said, "‘Ifar’ means that after grafting the date palm tree, they would leave it for forty days and would not water it after grafting." The man said, "(The incident is that) I found a man with my wife." The Prophet (peace and blessings be upon him) asked: "Her husband was of yellow complexion, thin-legged, and had straight hair, while the one whom he accused of adultery was stout, dark-skinned, and had very curly hair." So the Messenger of Allah (peace and blessings be upon him) prayed: "O Allah! Make this matter clear." Then he made them both perform li'an (mutual cursing), and then the woman gave birth to a child resembling the man whom she was accused of committing adultery with.