Al-Sha'bi (may Allah have mercy on him) narrates that two brothers married two sisters, and (by mistake) each was sent to the other's wife. So, Sayyiduna Ali (may Allah be pleased with him) said: "They will be separated from each other, and each woman will be given her dowry, and neither man should approach his wife until the waiting period ('iddah) of her sister is completed, and both husbands will take back the dowry from the person who deceived them."