I know that Allaah The Almighty has created us for the sake of worshiping Him. However, a friend of mine put doubts in my mind about this. What is the evidence that supports this notion?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

There is no doubt that Allaah The Almighty has created mankind and the Jinn only for the sake of worshipping Him and this is an unquestionable fact in the religion. In fact, denying this or even having doubts about it is considered the type of disbelief that results in apostasy. Allaah The Almighty Says (what means): {And I did not create the jinn and mankind except to worship Me.}[Quran 51:56] Thereupon, the Muslim must be fully aware of his great duty towards Allaah The Almighty, which is to worship Him in full submission and obey His commands because His Lordship implies His worthiness of worship. As a matter of fact, even if He had not sent messengers to command people to worship Him, He would still have been worthy of worship and glorification because of the countless blessings He has endowed  upon His slaves, starting from the blessing of creation and the other blessings that follow.

Allaah The Almighty Says (what means): {And if you should count the favors of Allaah, you could not enumerate them. Indeed, Allaah is Forgiving and Merciful.}[Quran 16:18] Nevertheless, you should not have had doubts about this because this is one of the fundamentals of Islam. Therefore, we advise you to learn about all your religious duties and the rulings and beliefs of Islam and to clarify to your friend that denying this unquestionable issue or having any doubts about it is considered apostasy and he should thus return to Allaah The Almighty in repentance.

And Allaah Knows best.