Assalamualaikum ustaz. What is the ruling for a woman to wear niqab (purdah) when she is praying?
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions and all those who follow his footsteps until the Last Day.
Covering aurah for Muslim women is an obligation in religion. The obligation is to protect the honor of women and subsequently elevates the status and level of women higher. This is in line with one of the purposes of why the Prophet PBUH was sent which is to elevate the status of women themselves who were oppressed during the jahiliyyah times.
Referring to the above query, wearing niqab or purdah is one of the best ways in the chapter of covering the aurah of women. Thus, the ruling of wearing niqab or purdah is sunnah and prioritized for women.
However, wearing niqab or purdah in prayer is different from the ruling of wearing it at other times. This matter is explained in the book Kifayatu al-Akhyar as the following: It is makruh to pray while wearing clothing that has pictures or drawings. It is also makruh for women to wear niqab (purdah) when praying except if the situation in the mosque where there are ajnabi men who don’t guard their sight. However, if there is a concern of harm, then it is prohibited for them to take off their niqab (purdah). 
While in the book al-Iqna’, it is explained as the following: “It is makruh to pray while wearing clothing with pictures, or clothing with drawings on them or women wearing niqab (purdah) except when there are men who don’t guard their vision, then it isn’t necessary for them to take off the niqab (purdah) and obligatory for them to cover.” 
Thus, according to the above statement, wearing niqab or purdah for women when they are praying is makruh. Although, if there is a reasonable reason, then it is permissible. The same applies to wearing facemasks during the COVID-19 pandemic. It is permissible.
Considering the situations in mosques and suraus in Malaysia, the praying place for women are usually closed off from men. Hence, the issue of fitnah discussed doesn’t arise.