What is the ruling on someone who told his wife, "You are forbidden to me like my sister for a month," while he did not know that this constituted dhihar, and this occurred in a state of intense anger, then he had intercourse with her three days after saying that? Does the expiation for dhihar become incumbent upon him?

This statement clearly indicates a temporary ẓihār, and the husband is obligated to pay the expiation for ẓihār if he has intercourse with his wife before the specified period ends. The husband's anger or ignorance of the Sharia ruling does not prevent the occurrence of ẓihār. Therefore, he must refrain from having intercourse with her until the month concludes, and then perform the expiation for ẓihār mentioned in the words of Allah Almighty: "And whoever does not find [a slave to free] - then [he must fast for] two consecutive months before they touch one another. And whoever is unable to do so - then [he must feed] sixty needy persons." If he has intercourse with his wife before performing the expiation, the expiation remains binding upon him, and his wife remains unlawful to him until he performs the expiation.