Does a divorce occur with the statement, "My wife, so-and-so, is triply divorced if you take your phone tonight," if the brother takes the phone at night, given that the intention was not divorce but rather to show seriousness in preventing the brother from taking the phone?

What happened on your part was a conditional divorce of your husband with three pronouncements (triple divorce) tied to your brother taking the mobile phone. What you conditioned the divorce upon has indeed occurred. Therefore, the triple divorce takes effect according to the majority of jurists. However, Sheikh Al-Islam Ibn Taymiyyah holds that if the husband did not intend divorce, it does not occur, and he is obligated to offer an expiation for an oath. If he did intend it, then a single divorce takes effect. Since there is a difference of opinion on this matter, it is advisable to consult the Sharia court, as a judge's ruling resolves such disputes. Anger does not prevent the occurrence of divorce unless the person is unaware of what he is saying. Similarly, returning the mobile phone does not prevent the breach of the condition. One should be wary of anger and avoid using divorce pronouncements.