The Prophet was sent to all of Mankind

Allah says to His servant and Messenger Muhammad:

وَمَا أَرْسَلْنَاكَ إِلَّا كَافَّةً لِّلنَّاسِ بَشِيرًا وَنَذِيرًا ...

And We have not sent you except as a giver of glad tidings and a warner to all mankind,

i.e., to all of creation among those who are accountable for their deeds.

This is like the Ayah:

قُلْ يَأَيُّهَا النَّاسُ إِنِّى رَسُولُ اللَّهِ إِلَيْكُمْ جَمِيعًا

Say: "O mankind! Verily, I am sent to you all as the Messenger of Allah.'' (7:158)

تَبَارَكَ الَّذِى نَزَّلَ الْفُرْقَانَ عَلَى عَبْدِهِ لِيَكُونَ لِلْعَـلَمِينَ نَذِيراً

Blessed be He Who sent down the Criterion to His servant that he may be a warner to the all creatures. (25:1)

... بَشِيرًا وَنَذِيرًا ...

a giver of glad tidings and a warner means,

to bring the glad tidings of Paradise to those who obey you and to warn of the fire of Hell to those who disobey you.

This is like the Ayat:

... وَلَكِنَّ أَكْثَرَ النَّاسِ لَا يَعْلَمُونَ ﴿٢٨﴾

and most of men know not.

وَمَآ أَكْثَرُ النَّاسِ وَلَوْ حَرَصْتَ بِمُؤْمِنِينَ

And most of mankind will not believe even if you desire it eagerly. (12:103)

وَإِن تُطِعْ أَكْثَرَ مَن فِى الاٌّرْضِ يُضِلُّوكَ عَن سَبِيلِ اللَّهِ

And if you obey most of those on the earth, they will mislead you far away from Allah's path. (6:116)

Muhammad bin Ka`b said concerning the Ayah: وَمَا أَرْسَلْنَاكَ إِلَّا كَافَّةً لِّلنَّاسِ (And We have not sent you except to all mankind) meaning,

to all the people.

Qatadah said concerning this Ayah,

"Allah, may He be exalted, sent Muhammad to both the Arabs and the non-Arabs, so the most honored of them with Allah is the one who is most obedient to Allah.''

In the Two Sahihs it was reported that Jabir, may Allah be pleased with him said,

"The Messenger of Allah said:

أُعْطِيتُ خَمْسًا لَمْ يُعْطَهُنَّ أَحَدٌ مِنَ الْأَنْبِيَاءِ قَبْلِي: نُصِرْتُ بِالرُّعْبِ مَسِيرَةَ شَهْرٍ، وَجُعِلَتْ لِيَ الْأَرْضُ مَسْجِدًا وَطَهُورًا، فَأَيُّمَا رَجُلٍ مِنْ أُمَّتِي أَدْرَكَتْهُ الصَّلَاةُ فَلْيُصَلِّ، وَأُحِلَّتْ لِيَ الْغَنَائِمُ وَلَمْ تَحِلَّ لِأَحَدٍ قَبْلِي، وَأُعْطِيتُ الشَّفَاعَةَ، وَكَانَ النَّبِيُّ يُبْعَثُ إِلَى قَوْمِهِ خَاصَّةً وَبُعِثْتُ إِلَى النَّاسِ عَامَّة

I have been given five things which were not given to any of the Prophets before me.

*

I have been aided by fear (the distance of) a month's journey.
*

The entire earth has been made a Masjid and a means of purification for me, so that when the time for prayer comes, any man of my Ummah should pray.
*

The spoils of war have been made permissible for me, whereas they were not permitted for any before me.
*

I have been given the power of intercession; and
*

the Prophets before me were sent to their own people, but I have been sent to all of mankind.''

It was also recorded in the Sahih that the Messenger of Allah said:

بُعِثْتُ إِلَى الْأَسْوَدِ وَالْأَحْمَر

I have been sent to the black and the red.

Mujahid said,

"This means to the Jinn and to mankind.''

Others said that it meant the Arabs and the non-Arabs.

Both meanings are correct.