What is the ruling of the Shari'ah concerning a man who committed adultery with a woman and she became pregnant by him, then he contracted a legal marriage with her without anyone knowing about the adultery, and she gave birth to a child whom he attributed to himself, considering him a legitimate child?

The man must offer sincere repentance and completely abandon the immoral act, showing remorse and a firm resolve not to return to it. His marriage to the girl who became pregnant by him through adultery is invalid according to the majority of scholars, because they stipulate that the adulteress must not be pregnant for the marriage to be valid, in order to prevent the mixing of lineages. The child resulting from adultery is not attributed to him, and he is not permitted to mix with his daughters. Some scholars differed and permitted marriage in this situation, such as Abu Hanifa, and they held that the child is attributed to the adulterer. The preponderant view is that of the majority of scholars, but if some scholars issue a fatwa (definition) validating the marriage and establishing the lineage to avoid a greater harm, then they are permitted to do so.