The Messenger is only charged with delivering the Message

Allah says,

فَذَكِّرْ إِنَّمَا أَنتَ مُذَكِّرٌ ﴿٢١﴾

لَّسْتَ عَلَيْهِم بِمُصَيْطِرٍ ﴿٢٢﴾

So remind them -- you are only one who reminds. You are not a Musaytir over them,

meaning, "O Muhammad! Remind the people with what you have been sent with to them.''

فَإِنَّمَا عَلَيْكَ الْبَلَـغُ وَعَلَيْنَا الْحِسَابُ

your duty is only to convey (the Message) and on Us is the reckoning. (13:40)

Then Allah says, لَّسْتَ عَلَيْهِم بِمُصَيْطِرٍ You are not a Musaytir over them.

Ibn `Abbas, Mujahid and others said,

"You are not a dictator over them.''

This means that you cannot create faith in their hearts.

Ibn Zayd said,

"You are not the one who can force them to have faith.''

Imam Ahmad recorded from Jabir that the Messenger of Allah said,

أُمِرْتُ أَنْ أُقَاتِلَ النَّاسَ حَتْى يَقُولُوا: لَا إِلهَ إِلَّا اللهُ،

فَإِذَا قَالُوهَا عَصَمُوا مِنِّي دِمَاءَهُمْ وَأَمْوَالَهُمْ إِلَّا بِحَقِّهَا، وَحِسَابُهُمْ عَلَى اللهِ عَزَّ وَجَل

I have been commanded to fight the people until they say La ilaha illallah (none has the right to be worshipped except Allah).

So if they say that, they have safeguarded their blood and wealth from me - except for what is rightfully due from it - and their reckoning is with Allah, the Mighty and Majestic.''

Then he recited,

فَذَكِّرْ إِنَّمَآ أَنتَ مُذَكِّرٌ - لَّسْتَ عَلَيْهِم بِمُسَيْطِرٍ

So remind them - you are only one who reminds. You are not a dictator over them -

This is how Muslim recorded this Hadith in his Book of Faith, and At-Tirmidhi and An-Nasa'i also recorded it in their Sunans in the Books of Tafsir.

This Hadith can be found in both of the Two Sahihs.