Actually it is assumed people already know the existance of Allah in his/her Fitrah.

 

The messengers were sent as a guide as how to establish the worship of Allah whilst living in this world and being of the successful.

 

So like every test we must have a teacher and a book on the subject. The prophets are our teachers and the Book is the Quran. And knowledge mandates action.

 

And in every verse in the Quran it is a benefit for ourselves and the only action which is for Allah is the prayer. And even then we still benefit! So people who strive due to greed, wealth, status and pride are only harming themselves yet they do not realize it!

 

Maryum : Umm Hasan bint Abdullah Alshabrawishi