Husband making his wife unlawful for him like his mother if he marries again

Q: Some years after my marriage to my first wife, she asked me to say that she would be to me like my mother if I married again. She wanted to guarantee that I would not marry another woman. I said these words to please her while being unaware of their ruling. However, I have recently found out that this statement is very significant even though when I uttered it I was unaware of the ruling; and I am illiterate. Now I want to marry another woman, but this statement prevents me from doing this. It is worth mentioning that I will never (Part No. 20; Page No. 302) neglect my duties towards my first wife.I am asking about the Kaffarah (expiation) of this statement, which I uttered while not understanding its ruling. I would like to inform you that I suffer from pneumonitis and I am not recommended to observe Sawm (Fast) during Ramadan according to the doctors' report. I wish to know the correct way that guides me to the good In Sha'a-Allah (if Allah wills). May Allah guide you to what is beneficial to this Ummah (nation based on one creed).

A: There is no problem if you get married, but then you should not have any sexual relations with your first wife until you make Kaffarah of Zhihar (a man likening his wife to an unmarriageable relative), which is emancipating a believing slave. If this is not available, you should observe Sawm (Fast) for two consecutive months before approaching your wife. If you are unable to do so, you must feed sixty Miskins (needy persons), by giving each one half a Sa` (1 Sa`=3 kg. Approx.) of wheat, dates, rice, or any of the staple food available. Allah (Exalted be He) says: And those who make unlawful to them their wives by Zihâr and wish to free themselves from what they uttered, (the penalty) in that case is the freeing of a slave before they touch each other. That is an admonition to you (so that you may not repeat such an ill thing). And Allâh is All-Aware of what you do. And he who finds not (the money for freeing a slave) must fast two successive months before they both touch each other. And he who is unable to do so, should feed sixty Miskîns (poor). That is in order that you may have perfect Faith in Allâh and His Messenger. These are the limits set by Allâh. And for disbelievers, there is a painful torment. Moreover, you should make Tawbah (repentance to Allah) and ask for Allah's Forgiveness because of what you have done. (Part No. 20; Page No. 303) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.