the time of adultery, and it is possible for him to negate it, it is incumbent upon him to accuse her of adultery (qadhf) and negate her child; because this is equivalent to certainty that the child is from the adulterer. If he does not negate it, the child is attached to him, it is attributed to him, he inherits from his relatives and they inherit from him, and he would look upon his daughters and sisters, which is not permissible. Therefore, it is obligatory to negate it to remove this. If she acknowledges the adultery and he is convinced of the truthfulness of her admission, it is the same as if he had seen it.
The second type is that he sees her committing adultery or her adultery is proven to him, and there is no child whose lineage would be attached to him, or there is a child but he does not know if it is from adultery, or a trustworthy person who confirms it informs him of her adultery, or it becomes common among people that a certain man engages in immorality with a certain woman, and he witnesses him with her, or entering to her or leaving from her, or he strongly suspects her immorality; in this case, he may accuse her (qadhf). This is because it is narrated from Abdullah that a man came to the Prophet (peace and blessings of Allah be upon him) and said: "What do you think of a man who found a man with his wife? If he speaks, you punish him; if he kills, you kill him; and if he remains silent, he remains silent out of rage (3)." He mentioned that he speaks or remains silent, and the Prophet (peace and blessings of Allah be upon him) did not rebuke him for it. Also, because the Prophet (peace and blessings of Allah be upon him) did not rebuke Hilal and al-'Ajlani for their accusation when they saw it (4). If he remains silent, it is permissible, and that is better, because he can separate from her by divorcing her, and in that, there is concealment for her and concealment for himself, and there is no child that needs to be negated.
The third case is forbidden, which is anything other than that, such as accusing his wives or strangers; for it is one of the major sins. Allah the Almighty said: {Indeed, those who [falsely] accuse chaste, unaware, believing women are cursed in this world and the Hereafter; and they will have a great punishment} [Surah An-Nur 23] (5). The Prophet (peace and blessings of Allah be upon him) said: "Any woman who brings into a people someone who does not belong to them, she has no connection with Allah in anything, and Allah will never admit her into His Paradise. And any man who denies his child while he is looking at him, Allah will veil Himself from him and disgrace him before the heads of the first and the last." Narrated by Abu Dawood (6).
(3) Recorded by Muslim, in: Kitab al-Li'an. Sahih Muslim 2/1133. And Abu Dawood, in: Bab fi al-Li'an, from Kitab al-Talaq. Sunan Abi Dawood 1/522. And Ibn Majah, in: Bab al-Li'an, from Kitab al-Talaq. Sunan Ibn Majah 1/669. And Imam Ahmad, in: Al-Musnad 1/421, 422, 448. (4) The takhrij (verification of source) for their hadith previously appeared in: 8/373, 10/330. (5) Surah An-Nur 23. (6) In: Bab al-Taghliz fi al-Intifa', from Kitab al-Talaq. Sunan Abi Dawood 1/525.