This is a treatise we have written concerning humility (Khushu) and the hearts meakness and breaking (inkisar) before the Lord.
The basic meaning of Khushu, is the softness of the heart, its being gentle, still, submissive, broken, and yearning. When the heart is humble, so too is the hearing, seeing, head, and face; indeed all the limbs and their actions are humbled, even speech. This is why the Prophet would say in his bowing (ruku), 'My hearing, sigh, bones, and marrow are humbled to You,' another narration has, 'and whatever my foot carries.
One of the Salaf saw a man fidgeting in his prayer and remarked, 'If the heart of this person was humble, so too would his limbs be.' The source of Khushu, that takes place in the heart is the gnosis of Allah's greatness, magnificence, and perfection. The more gnosis a person has of Allah, the more Khushu he has. The greatest action of worship which manifests the Khushu, of the body to Allah is the prayer (salah). Allah has praised those who have Khushu, in the prayer.
al-Hasan, may Allah have mercy on him, said, 'When you stand in prayer, stand in due obedience as Allah has ordered you, beware of negligence and looking (here and there), beware that Allah be looking at you while you are looking at something else, asking Allah for Paradise and taking refuge with Him from the Fire, yet your heart is heedless, not knowing what the tongue is saying.
Hudhayfah said, 'The first thing you will lose of your religion will be Khushu and the last thing you will lose of your religion will be the prayer, and it is well possible that there is no good in a person who prays, and soon will come a time when you shall entre a large Masjid and not see a single person with Khushu.
This small treatise deals with the correct and accurate meaning of Khushu, and with three extremely beneficial appendixes.