Does a divorce take place and expiation become binding if the wife uses cooking water contaminated by mistake or forgetfulness, after the husband swore to divorce her if she did so intentionally?

Your saying to your wife: "By divorce, if you make it again, you are divorced" is an oath of divorce. If the wife does not use the water, nothing occurs. If she uses it, divorce occurs according to the majority of scholars. The Shafi'is hold that divorce does not occur if she did it out of forgetfulness. Sheikh al-Islam Ibn Taymiyyah holds that an expiation for an oath is due if the intention was to threaten or prevent, regardless of whether the wife did it intentionally or out of forgetfulness.