Translation of the verse 2 from Surah Al-Mu’minun : Number of verses 118 - - page 342 - Part 18.
Those who offer their Salat (prayers) with all solemnity and full submissiveness.
They who are during their prayer humbly submissive
(23:2) who *2 perform their Salat with humility: *3
*2) The noble characteristics of the Believers pointed out in vv. 2-9 are the arguments to prove the above assertion. In other words, it has been stated that people with such and such traits and qualities only can attain true success in this world and in the Hereafter.
*3) Khashi`un in the Text is from khushu (to bow down, to express humility) which is a condition of the heart as well as of the body. Khushu' of the heart is to fear and stand in awe of a powerful person, and khushu ` of the body is to bow one's head and lower one's gaze and voice in his presence. In Salat one is required to show khushu ` both of the heart and of the body, and this is the essence of the Prayer. It has been reported that when the Holy Prophet once saw a person offering his Prayer as well as playing with his beard, he remarked: "Had he khushu ` in his heart, his body would have manifested it. "
Though khushu ` is actually a condition of the heart, as stated by the above tradition, it is manifested by the body as a matter of course. The Shari `ah has enjoined certain etiquette which, on the one hand, helps produce khushu ` in the heart, and on the other, helps sustain the physical act of the Prayer in spite of the fluctuating condition of the heart. According to this etiquette, one should neither turn to the right or left, nor raise one's head to look up: one may, however, look around from the corner of the eye, but as far as possible, one must fix the gaze on the place where the forehead would rest in prostration; one is also forbidden to shift about, incline side ways, fold the garments or shake off dust from them. It is also forbidden that while going down for prostration, one should clean the place where one would sit or perform prostration. Similarly it is disrespectful that one should stand stuffy erect, recite the verses of the Qur'an in a loud resounding voice, or sing them, or belch or yawn repeatedly and noisily. It has also not been approved that one should offer the Prayer in a hurry. The injunction is that each article of the Prayer should be performed in perfect peace and tranquillity, and unless one article has been completely performed, the next should not be begun. If one feels hurt by something during the Prayer, one may cast it aside by one hand, but moving the hand repeatedly or using both the hands for the purpose is prohibited. with this etiquette of the body, it is also important that one should irrelevant things during the Prayer. If thoughts come to the mind intention, it is a natural human weakness, but one should try one's
Along avoid thinking without one's utmost that the mind and heart are wholly turned towards Allah, and the mind is in full harmony and tune with the tongue, and as soon as one becomes conscious of irrelevant thoughts one should immediately turn the attention to the Prayer.
Source : Al-Mu’minun Verse 2: They who are during their prayer humbly submissive