Distinguishing Between Divorce and Prohibition

Question:
He said to his wife: "You are forbidden to me," but some people told him: "She will not remain forbidden to you unless you said to her: 'You are divorced.' So, is there a difference between 'forbidden to me' and 'you are divorced'?"

Answer:
Divorce is one thing, and prohibition is another. If he says: "You are forbidden to me," he owes an expiation, and she is not divorced; she remains his wife. If he says: "You are forbidden to me," or "You are to me like my mother," or "You are to me like my sister," or "You are to me like my daughter," intending to forbid her to himself, then he owes an expiation. The expiation is freeing a believing slave. If he cannot find one, he must fast for two consecutive months. If he is unable to do so, he must feed sixty poor people, which is thirty sa' (a dry measure of about 3 kg), with each person receiving half a sa', which is one and a half kilograms of the local staple food, such as dates, rice, or wheat, before he touches her, before he has any contact with her. This is the ruling.
As for if he says: "You are divorced," this is one divorce if nothing preceded it. It is one divorce, and he can take her back, and she is his wife. He owes no expiation, and nothing is required of him.

Question: He only said to her: "You are forbidden to me," did he not make it conditional?

Answer: "You are forbidden to me" has the ruling of zihar (likening one's wife to a forbidden relative), just as if he said: "You are to me like my mother's back."