Al-Hafidh Ibn Rajab (d. 795H) - rahimahullaah - said:
"So know that the world - and whatever is above it and below in the water - will not be corrected except when the actions of its people are all for Allaah. The actions of the body follow on from the actions and intentions of the heart. So when the actions and intentions of the heart are purely for Allaah alone, then it is corrected, and likewise the actions of the body will also be correct. However, if the actions and intentions of the heart are for other than Allaah, then it is corrupted, and likewise the actions of the body will be corrupted in proportion to how much the heart is corrupted." [Jaami` al-`Uloom wal-Hikam p. 120].
And he said, "Hearts will not be corrected until the ma`rifah (knowledge and realisation) of Allaah - being in awe of His greatness, loving Him, fearing Him, hoping in Him, relying and trusting in Him - is not firmly implanted in them. This is the reality of Tawheed and the meaning of the saying: laa ilaaha illallaah (that none has the right to be worshipped except Allaah). Thus, hearts will not be corrected until Allaah is made the ilaah (deity) to be known, to be loved, feared and hoped in, and that He - along with this - becomes the only ilaah (deity) worthy of this, without associating any partner to Him in this." [Jaami` al-`Uloom wal-Hikam p. 120].
Indeed, we may begin to appreciate the greatness of Allaah - the Most High's - and being in awe of Him, by considering some narrations regarding what He - the Most High - has created:
The Prophet, sallallahu `alayhi wa sallam said:
"Indeed I see what you do not see and hear what you do not hear. Heaven has groaned, and it has a right to do so. By Him in Whose Hand is my soul! There is not in heaven a space equivalent to four fingers, except that an angel has prostrated his forehead to Allaah in it. By Allaah! If you knew what I know, you would laugh little and weep alot, and you would not take delight in women in their beds, but rather would go to the wilderness and implore Allaah for help." [Hasan: Related by ibn Maajah (4190) and at-Tirmidhee (2/51) who authenticated it, from Abu Dharr radhiallahu `anhu]
He sallallahu `alayhi wa sallam said:
"The seven Heavens compared to the Kursee is like a ring in which is thrown into a desert. And such is the magnitude of the `Arsh (the Throne of Allah) compared with the Kursee." [Saheeh: Related by Ibn Abee Shaybah in Kitaabul `Arsh (1/114), and Al Bayhaqee in Al-Asmaa was-Sifaat (p. 290), from Abu Dharr radhiallahu `anhu. The hadeeth is authentic due to its various routes of transmission - as Shaykh al-Albaanee has explained in As-Saheehah no 109.]
And He sallallahu `alayhi wa sallam said:
"Al-Baytul-Ma`moor is in the seventh heaven [directly above the Ka`bah]. Each day seventy thousand angels enter it, and they will not return until the Day of Resurrection." [Saheeh; Related by Abu Daawood (no 4727) and al-Bayhaqee in al-Asmaa was-Sifaat (no. 398), from Jaabir radhiallahu `anhu. It was authenticated by Imaam adh-Dhahabee in al-`Uluww (p. 58).
So: "the need of the servants for this (type of) knowledge is greater than every other need; and it is the most necessary of all things for hem, since there is no life for the hearts, nor any delight, nor any tranquility, except through knowing their Lord, the only One Who deserves to be worshipped, their Creator - with His Names, His Attributes and His Actions, and that He - along with all that - is more beloved to the person than anything else. So man's striving is with regards to everything that will draw him nearer to Allaah, to the exclusion of the creation. So the people who know Allaah the best, are the ones who best follow the way to Him; and know best what lies at the end of the way."