One of the fundamental characteristics of unbelievers is their arrogance. It is that which has led them to refuse to obey the messengers of Allah, and to resort to excuses in order not to do so. One such excuse was that they would only obey these messengers if they were more than human. Yet, the Prophet (PBUH) reminded his people that he was human, a mere servant of Allah, and that all other such expectations were groundless, but that they should turn to Allah. Allah gave the Prophet (PBUH) the following commands in the Quran:
The Prophet (PBUH) told his people that he was also commanded to be one of the Muslims and to obey Allah, and that he was responsible for warning the unbelievers, but that he could not be held responsible for their choices. The verses in question read:
"I have simply been ordered to worship the Lord of this land which He has declared sacred-everything belongs to Him-and I have been ordered to be one of the Muslims and to recite the Quran." Whoever is guided is only guided to his own good; if someone is misguided just say, "I am only a Warner." Say: "Praise be to Allah. He will show you His Signs and you will recognize them. Your Lord is not unaware of what you do." (Surat an-Naml: 91-93)
source : tebyan