Am I obligated to offer expiation for insisting that my wife abort a fetus that was more than two months old, especially since I deeply regret it and this happened approximately thirteen years ago?

It is permissible to regulate pregnancy for the sake of breastfeeding and the well-being of the child and mother. The husband must repent for his crime against the fetus, as anger is not a justification for prohibited actions. If a fetus is aborted after forty days, a ghurrah is required, which is a male or female slave, and its value is one-tenth of the mother's diyah (blood money). This ghurrah is obligatory upon the person who directly performed the abortion. The one who directly performed the abortion must also offer kaffarat al-qatl (expiation for killing), which is freeing a believing slave or fasting for two consecutive months. As for the husband, if he did not directly perform the abortion but ordered it, neither diyah nor kaffarah is obligatory upon him. However, he is sinful and must repent, as the ruling is attributed to the direct perpetrator when both a direct perpetrator and an instigator are involved.