A vow to fast three days of every lunar month, but he now works in the desert and finds fasting difficult, so what is required of him?

Question:
I am a Sudanese Muslim who works as a digger in the desert. I vowed to the Most Merciful to fast three days of every month, of every lunar month. I was consistent with this fasting until I took up work in the desert, where the nature of the work is arduous. I fasted the days of Shawwal and found it very difficult, and I did not fast the three or four months that followed. I hope you will guide me regarding the expiation for the past or the alternative to fasting under these circumstances. The reason for the vow is that I asked Allah, the Exalted and Almighty, to grant me success in my profession, and praise be to Allah, by His will I was successful, and I resolved to fulfill the vow.

Answer:
Yes. The Prophet (peace and blessings be upon him) said: You vowed to fast if you obtained what you sought, and you have obtained it, so it is obligatory for you to fulfill the vow. You mentioned that you began to fulfill it and fasted several times, but during your work in the desert, fasting became difficult for you.
We say it is obligatory for you to fast, even if you are in the desert, and even if there is a hardship that is bearable. If the hardship is bearable, it is obligatory for you to fast, even with the bearable hardship. Immediately, he should fast the upcoming months and continue. He mentions that he fasts several days of every month, and he did not specify a particular year, so it appears that it is continuous. It is obligatory for him to continue every month and fast, acting upon his vow and fulfilling his vow, even if he encounters a severe hardship in it, but he can bear it. However, if the matter reaches the point of danger, and he is unable to fast, for example, or if fasting would result in danger to his life, then in that case he breaks his fast and pays the expiation for an oath for the days he was unable to fast. Yes. The expiation for an oath is freeing a slave if he finds one, or feeding ten poor people, or clothing them; he has the choice among these three things. If he cannot do any of the three things, he moves to fasting three days. This is for the days he was unable to fast. If, after that, this excuse is removed and he is able to fast later, then he fasts. Yes. As for the days you left in the past and did not fast, as we mentioned, you perform the expiation for an oath for them?