The main Objective of Revelation is that Allah be worshipped

Allah commands His Messenger to say to the idoators:

إِنَّمَآ يُوحَى إِلَىَّ أَنَّمَآ إِلَـهُكُمْ إِلَـهٌ وَحِدٌ فَهَلْ أَنتُمْ مُّسْلِمُونَ

Commentary

وَمَا أَرْ‌سَلْنَاكَ إِلَّا رَ‌حْمَةً لِّلْعَالَمِينَ (And We have not. sent you but as mercy for all the worlds. - 21:107) عَالَمِينَ is plural of عَالَم which means 'world' and includes all creatures including humans, animals, plants, Jinns etc. In order to properly understand the meaning of the verse one should also understand that the true essence of the entire universe is the invocation of Allah Ta` ala and His worship. When this essence departs from this world and no one is left to worship Allah, everything in it will perish. In other words that is the day when Qiyamah would occur. When it is understood that the invocation and worship of Allah Ta` ala is the essence of all living things, then the reason for describing the Holy Prophet ﷺ as mercy to the Worlds becomes obvious because it is his teachings and the purity of his personal life alone which keep alive the worship of Allah Ta` ala until Qiyamah. That is why he declared "I am the blessing sent by Allah اَنَا رَحمَۃُ مُھدَاۃُ (Ibn ` Asakir quoting Abu Hurairah). Sayyidna Ibn ` Umar , has reported that the Holy Prophet ﷺ said اَنَا رَحمَۃُ مُھدَاۃُ بِرَفعِ قَومِ وَخفضِ آخرِینَ that is "I am the blessing sent by Allah so that I lift up the people (who obey Allah) and humble the other people (who disobey Allah). (Ibn Kathir)