Q 1: What is the ruling on
Khushu` (the heart being submissively attuned to the act of worship) during performing Salah (Prayer)?
Besides, how can I refute the saying that Khushu` in Salah is Sunnah (acts, sayings or approvals of the Prophet) not Wajib (obligatory)?
There are two different kinds of Khushu`: Wajib and Mustahab (desirable). The Khushu` which is Wajib is to maintain tranquility while doing all the acts of Salah so that they are done fully and perfectly. This kind of Khushu` is that which is meant by the Saying of Allah:
Successful indeed are the believers.
Those who offer their Salât (prayers) with all solemnity and full submissiveness.
Also, it is that which is meant by the Hadith of the Prophet (peace be upon him) about the person who wrongly performed his Salah.On the other hand, the Khushu` which is Mustahab is to perform Salah perfectly along with all its Mustahab acts and sayings.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.