Is it permissible to return the wife to the bond of marriage after the husband uttered "my wife is divorced from me" for the first time while he was abroad, then two days later he returned her to his bond three times and cohabited with her, with her knowledge of the divorce and the return after two weeks?

Your statement: "My wife is divorced from me" is an explicit divorce, and divorce takes effect by it. The presence or knowledge of the wife is not a condition for its occurrence. Your taking her back before the expiration of her 'iddah is valid, and the wife's knowledge or consent is not a condition for the validity of the return. Thus, your return is valid, your wife is under your marital authority, and one divorce has been counted against you.