Lian (mutual imprecation)

because the revocable divorce does not annul the marital bond. And if he said to her: "O adulteress, you are divorced three times", there is neither punishment nor lian, for his words "O adulteress" made lian obligatory, not the punishment, for he slandered his wife; and when he said "you are divorced three times", he annulled the marital bond, and lian applies only to wives. And if he said to her: "You are divorced three times, O adulteress", the punishment becomes obligatory and not lian, for he slandered her after separation (iban), and she became a stranger after the separation, and the slander (of the stranger)

The punishment (hadd) becomes obligatory for his slander, lian having been established only to avert the punishment together with the denial of lineage. They sometimes argued by what Amr ibn Shu'ayb reported, from his father, from his grandfather: the Messenger of Allah (peace and blessings of Allah be upon him) said: "No lian between four: two slaves and two disbelievers". And the majority hold that it is an oath, though it be called testimony, for none testifies for himself. As for testimony being sometimes expressed by oath, that is clear in His words, the Most High: "when".