Allah [may He be Glorified] said: “And We have not sent you (O Muhammad) except as a giver of glad tidings and a Warner to all mankind, but most of men know not” (34:28)
In this verse Allah states that He did not send His Messenger Muhammad (peace be upon him) except for giving the glad tidings of reward for all mankind and to inform them about the acts bringing about such a reward.
He is also sent to forewarn them of God’s punishment, and make known to them acts that may warrant such reprisal.
On the Authority of Abu Hurairah (may Allah be pleased with him) who reported that the holy Prophet said: “By Allah in whose hands my soul is, if anyone of this Ummah (nation) hears about me whether he is a Jew or a Christian and dies without believing in my Message, will be among the dwellers of the Hell-fire.” [Sahih Muslim, the Book of Faith, Hadith no.153]
The word “Ummah” in this Hadith means those whom the call to Islam has reached.
The phrase “If anyone of this Ummah hears about me” means those who lived at the time of the Messenger of Allah (peace be upon him), as well as those who will come after him till the Day of Judgement. In fact, all of them should follow his way. Mentioning just the Jews and the Christians in this context however serves as an alarming note for the followers of other faiths; since the Jews and the Christians have Divine Books while others do not. As the people of the Book are mentioned in this respect, though they are endowed with books of guidance, it thus follows that others, who have not any divine books, are also involved with greater reason. Allah knows best. [An-Nawawi’s Commentary on Sahih Muslim, Vol. II, Hadith p. 188]
Source: QuranComplex