What is the first (religious)obligation on Allah's servants?

What is the first (religious)obligation on Allah's servants?

Answer

 - The first religious obligation on worshippers is to realize the purpose for which Allah the Almighty created them; and for which He took their covenant and sent them His Messengers and Books; and for which He created this present life, the Hereafter, Paradise and Hell-fire; and for which the Inevitable would come true; and the Event would befall; and for which the Balance is set and the Records fly; and for which there would be either happness or misery; and according to which the lights would be divided, for any to whom Allah gives not light, there will be no light for him.