What should one do who intended to combine the fasting of an atonement for an oath with the fasting of the six days of Shawwal, then learned that it is not permissible to combine them due to the difference in intention and the necessity of sequential fasting for the atonement? And does he need to repeat the fasting of the atonement and the six days of Shawwal? And what is counted for him from the days he has already fasted?

If you are unable to pay the expiation for an oath to the poor, then you move on to fasting. It is permissible to fast discontinuously according to the majority of scholars, and it is necessary to make the intention to fast for expiation from the night. As for combining the fasting for the expiation of an oath with the fasting of the six days of Shawwal, there is a difference of opinion among scholars. However, if you intend to fast for the expiation of an oath, you may attain the reward of fasting the six days of Shawwal according to some scholars.