What is the ruling on a man who said to his wife in a moment of anger, "You are forbidden to me," intending discipline and not zihar or divorce, then had intercourse with her after seven days? And is he required to offer an expiation?

Prohibiting one's wife becomes a divorce if the husband intended divorce, and zihar (a form of unlawful repudiation) if he intended it, and an oath if he intended it as an oath or to urge an action or abstention from something. As long as you did not intend divorce or zihar, but rather intended discipline and reprimand, then it is an oath that requires an expiation: feeding ten poor persons, or clothing them, or fasting three days if you cannot find the means for the former.