Does a divorce pronounced as an oath, saying "by three divorces" to one's sister that he would not speak to her, take effect, knowing that the one who swore the oath was extremely angry and unaware of what he was saying?

The questioner reminds of the Prophet's (peace be upon him) advice: "Do not get angry." One should not swear except by Allah's name, and one should not make the husband's infallibility a means of pressure or exposure to doubt or the unlawful. It is not permissible for a Muslim to forsake his brother for more than three days. As for swearing by divorce in a state of extreme anger, the answer to this can be found in fatwas No. 35561 and No. 35574.