A promise to divorce

Q: I have a wife who bore me three children; the youngest of them is one year old. My wife is illiterate. I was working in the northeastern borders of the Kingdom of Saudi Arabia adjacent to Kuwait. I demanded to be transferred to the southern region so I could take care of my parents, who have no one to support them except me. By the Grace of Allah, Who knows the fraud of the eyes and all that the breasts conceal, then by the help of men in authority - may Allah protect them and (Part No. 20; Page No. 28) grant them success - I have been transferred to Al-Qunfudhah, which is about 160 km away from my house. My wife and children serve my parents while I go to work. I visit my family every weekend. My mother is an aged illiterate woman. She and my wife are engaged in disputes. They do not accept each other's advice. I built a small house for my mother at a distance of about 500 km from my house and I told her that everything will be brought to her ready made. My father is a wise and patient man. He always tries to reconcile their views, but my mother does not accept any fault from my wife. One day I returned from work and greeted my mother, who complained to me about my wife's behavior. I tried to advise her to be patient with my wife for the sake of my children as my wife takes care of them, but she burst into tears and blamed me. When she wept, I promised her that I will divorce her and told her to wait until the young child grows up.A month later, things were back to normal and my wife has started to treat my mother well, perhaps fearing the consequences of her ill-treatment of my mother. I have, thus, changed my mind as regards divorcing her. (Part No. 20; Page No. 29) I would like to know the ruling regarding what I did. Is there any sin on me regarding my relation with my wife? Should I keep my promise to my mother? May Allah safeguard you for what you do for all Muslims.