Amr ibn Shu'ayb narrates from his father, who narrates from his grandfather, that the Prophet Muhammad (peace be upon him) said: "When a woman claims divorce from her husband and presents a just witness regarding this, then an oath will be taken from her husband. If he takes the oath, the testimony of that witness will be considered invalid, and if he refuses to take the oath, his refusal will be considered as equivalent to a second witness, and the divorce given by him will be accepted."