What is the ruling of Islamic law regarding a man who divorced his wife twice, and then divorced her a third time in writing while he was angry, saying: "If you don't come, you are divorced by three"?

If the husband uttered a clear divorce statement over the phone for the first time, it is effective. As for the second, conditional divorce, the fatwa we follow is that it is effective, although there is a difference of opinion among scholars regarding distinguishing between conditioning for the purpose of enacting it or for threatening. Regarding the last time he conditioned a triple divorce in writing, if he intended divorce, it is effective. If he did not intend it, scholars have differed on whether writing is an implicit (kinayah) statement that requires intention for the divorce to take effect. Therefore, it is advisable to present the matter to trusted scholars in your country.