Three years ago, or even more, I vowed that if I was healed from a certain illness, I would pray two Rak‘ahs (units of prayer) every day for the sake of Allaah Almighty. After I went to the physician and started the treatment, I began to pray these two Rak‘ahs; however, I used to combine them with the two Rak‘ahs of the regular voluntary prayer that are performed after the Maghrib prayer. More precisely, I used to pray them with the intention of offering the regular voluntary prayer along with the intention of fulfilling the vow, but I did not pray them separately. Is this permissible? If not, then how can I expiate for this? Moreover, may I combine the Istikhaarah prayer with the regular voluntary prayers or should I perform them separately and then each of them has its reward?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

First of all, we would like to draw attention to the fact that it is disliked to make a vow. The vow that you have made is a conditional vow; if you were healed from the illness that you have mentioned, then it is obligatory upon you to fulfill it, otherwise you are not required to do anything. If you fall under the obligation of fulfilling the vow, then combining the intention of fulfilling the vow with the intention of performing the regular voluntary prayer does not clear you of your liability. Each of them is a separate act of worship. Therefore, combining both intentions in one prayer does not free you of your liability. Scholars held different opinions as to whether the two Rak‘ahs prayed in such a manner are considered a  fulfillment of the vow or the regular voluntary prayer or neither of them. That is why we believe that it is safer and more prudent to make up for the two Rak‘ahs of the vow for the whole period in which you combined the intention of fulfilling the vow and offering the voluntary prayer. If you are unable to specify the duration in which you combined both intentions, then continue to make up for it until you are almost certain that you have freed yourself of your liability. Be sure to not combine them in the future.

You may combine the Istikhaarah prayer and the regular voluntary prayer in one voluntary prayer, whether it is two Rak‘ahs or more, although it is better to single out each of them in a separate prayer because doing this involves more prayer, recitation, and remembrance of Allaah Almighty.

Allaah Knows best.