A man saying: “If I have intercourse with my wife, I will have intercourse with you, O my mother”

Question:
Honorable Shaykh. The professor says: I took my wife to her parents’ house before she gave birth, and then she stayed with her parents for a long time, so my mother kept reproaching me for that. I said to my mother, and I was angry, and I wanted to say: If I have intercourse with my wife, I will have intercourse with you, O my mother. Is this zihar or an oath, even though my intention was to please my mother? A long time has passed since this incident, so what is required of me, my brother? May Allah reward you with good.

Answer:
This is zihar. If he likens intercourse with his wife to intercourse with his mother, that is zihar. He must expiate for the zihar, and he must not have intercourse with his wife until he expiates for the zihar. He must free a slave, or if he cannot, he must fast for two consecutive months before he is able to have intercourse. If he cannot fast, he must feed sixty poor people.