Al-Qudoos is one of Allah's Most Beautiful Names:

Today, we are discussing the manifestations of Allah's Most Beautiful Name Al-Qudoos (the Holy, the All-Pure), and I would like first to mention an Ayah where this Name is mentioned. Allah the Almighty says:  

(Whatsoever is in the heavens and whatsoever is on the earth glorifies Allah, the King (of everything), the Holy, the All-Mighty, the All-Wise.)

[Al-Jumu'ah, 1]

The meaning of Al-Qudoos:

Al-Qudoos is derived from sanctity and purity. The purified land is the sacred one, and Al-Jannah is called the place of sanctity, because it is purified from all worldly defects. Our Master Jibrael (Gabriel) is called Ruh-ul-Qudus, because he is purified from all defects while revealing the Revelation. Allah the Almighty tells us in the following Ayah what the Angels said to Him:      

(While we glorify You with praises and thanks (Exalted be You above all that they associate with You as partners) and sanctify You." He (Allah) said: "I know that which you do not know.")

They meant to say, "O Allah, we purify ourselves and sanctify them to be qualified to approach You." Well, this is what man is supposed to do; he should purify himself to get a seat of truth (i.e. Paradise), near the Omnipotent King (Allah, the All-Blessed, the Most High, the Owner of Majesty and Honor). Hence, your main concern should be purifying yourself, in order to be with the Prophets, peace be upon them, the truthful, the martyrs and the righteous on the Day of Resurrection. Allah the Almighty says:
 

(And how excellent these companions are!)

[An-Nisa', 69]

Al-Qudoos is the One Who is sanctified from any description the senses can perceive, the mind can imagine, the illusions can be based on, the conscious can think of or the intellect can come up with. 
Al-Qudoos is the One Whose Divine Character is free from all needs and Whose Attributes are free from all defects. On the other hand, Allah's creation is not self-sufficient; no matter how knowledgeable, intelligent, powerful and oppressing man is, he becomes a weak person if he is dying for a drop of water to satisfy his thirst.  Regarding this point, a man once asked the Khalifah, "O Commander of the Believers, how much do you pay for this glass of water?" The Khalifah answered, "I pay half of my wealth." Then, the man asked, "How much do you pay to excrete it from your body?" The Khalifah answered, "I pay the other half of my wealth."    

Whoever comprehends this Name properly purifies his ownself from all forbidden lusts, purifies his money from Haram (unlawful) earning and purifies his time from wasting it in committing violations and so on. It is said, "Be keen on letting Allah sees you where you are supposed to act upon His Order and misses you where you are supposed to refrain from."  

Furthermore, whoever knows the meaning of Al-Qudoos never humiliates himself before any one. On the contrary, he elevates himself to his Lord. In other words, when man approaches Allah the Almighty, he never humiliates himself before any one. Moreover, whoever comprehends the meaning of Al-Qudoos lifts his aspiration till Allah the Almighty purifies him from all defects. As a result, he lowers his gaze from looking at forbidden things, and he protects his hearing from listening to forbidden things. 

In Ramadan, Al-Qudoos is manifested in purifying oneself from all dirts and defects when man approaches Allah, seeking His Protection. Consequently, man will be as sinless as the new-born baby when he fasts Ramadan out of sincere faith (i.e. belief) and prays Taraweeh (night prayers in Ramadan) hoping to get a reward from Allah.