Khushu in the Prayer
To the book:
Al-Khushuʿ in Ṣalāh: Presence of the heart therein before Allāh the Exalted in love and honor, fearing His punishment. While desiring the reward of the Ṣalāh to acquire a tranquil heart. Then one will have a peaceful soul and clear, balanced movements. So he focuses on all thoughts and actions as well as what's mentioned in Ṣalāh from the beginning until the end so as to make sure distracting thoughts and whims are not in the way. Thus khushuʿ is the spirit of the Ṣalāh and the main point in it. Alas, any Ṣalāh without khushuʿ is like a body without a soul in it.