What is the ruling on a vow that mentions prayer, and is expiation obligatory for abandoning these emphasized Sunnah prayers during periods of travel and pregnancy, especially given that one of them was specifically the Sunnah of Dhuhr? Is it obligatory to fulfill the vow during travel or not, and if it is, how is it done? Is it obligatory to adhere to all Sunnah prayers during periods of pregnancy, and what is the number of rak'ahs for the Sunnah of Dhuhr that must be adhered to?

According to the majority of scholars, a vow to pray two rak'ahs after Fajr is not valid due to the prohibition of performing voluntary prayers at this time. Vowing to perform Sunan (plural of Sunnah, recommended acts) obligates one to fulfill them, according to the more correct opinion. The preponderant opinion is that voluntary prayers are commendable during travel. If one vows to perform a Sunnah act, it becomes obligatory upon them to do so. The expiation for breaking a vow is the same as the expiation for breaking an oath. One must adhere to the vow in the future unless unable to do so. Scholars differ regarding making up a vow if its fulfillment becomes impossible. The Malikis do not consider making it up obligatory due to inability, but they do if it was intentionally abandoned. The Shafi'is consider making it up obligatory even with an excuse. The Hanbalis consider only expiation obligatory. Ibn Qudamah holds that expiation is for one who is permanently unable to fulfill the vow, but if the inability is temporary, one should wait for it to cease. For the Sunnah prayer of Dhuhr, it is permissible to suffice with four rak'ahs before it and two after it, though four before it and four after it is better. If one vows a specific number of rak'ahs, one must fulfill that specific number.