Answer
(Fatwa: 45/45/M=1432)
If the promise to Allah means that you swore and said: “In swear Allah, I will not commit such sin in my life again”, it took place. When you committed that sin, you broke your oath. Now it is necessary to pay its kaffarah. As much as oath you would break, that much kaffarah would be wajib. The kaffarah of oath is to feed ten poor persons two times meal or to give them dresses. And, if one is unable to do so he should keep three fasts consecutively.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband