What is meant here by “the inclusiveness of Islam” is that fact that Islam is for all times and places. Regardless of who a person may be or where he may be, Islam should be his religion and his way of life. This is just as much true for those who lived during the lifetime of the Prophet, may the mercy and blessings of God be upon him, or those who will live in 2525 (if God wills that there shall be such a year).
The correct understanding of this point revolves around a number of issues. The first important issue is that of the finality of prophethood as vested in the Prophet Muhammad. The second concerns the perfection of the religion and the manner in which it is able to guide humankind during all eras.
The Finality of Prophethood
God decreed that the Prophet Muhammad would be His final messenger. God says:
“Muhammad is not the father of any man among you, but he is the Messenger of God and the last of the Prophets. And God is Ever All-Aware of everything.” (Quran 33:40)
The Prophet Muhammad himself said:
“I have been sent to all of the creation and the prophets have been sealed by me.” (Saheeh Muslim)
Again, he said:
“The Children of Israel were led by the prophets; whenever a prophet died, a prophet succeeded (him). Lo! There will be no prophet after me” (Saheeh Al-Bukhari, Saheeh Muslim)
Thus, there finally came the Prophet who explicitly declared that he is the final prophet. The Prophets who came before the Prophet—as far as can be seen from what is narrated from them—did not make such a claim regarding themselves. Thus, for example, in Deuteronomy 18:17-19, God is telling Moses that He is going to send another messenger “like unto him” in the future. In the New Testament, in John 14:15-16, Jesus speaks of “another Comforter” being sent by God. (Also in John 16:7-8 and John 16:12-13 Jesus speaks of someone coming in the future.) On the other hand, the Prophet Muhammad made it very clear that no prophet would come after him.
Being sent as the final messenger for humankind, there had to be some aspects that were unique concerning this last Prophet. These aspects include:
First, since no one could come later to correct any mistakes or distortions, the revelation received by the last prophet had to be preserved in its pristine purity. It is obviously beyond the scope of this short article, but a study of the history of the Quran and Sunnah would demonstrate that both of them were minutely preserved.
Second, the nature of the “sign” of the last prophet would have to be different as well. This is because this sign would have to affect not only the people who were alive during the time of the prophet, but also all those who would come later. The “sign” of the Prophet Muhammad was the Quran, and its miraculous nature can still be appreciated today and will continue to be appreciated in the future.
Third, this final prophet could not simply be sent for one community among humankind—each then having their own final prophet and then differing with one another. This final prophet had to be sent for all of humankind, putting an end to the succession of prophets and being suitable for the world as a whole. The Prophet Muhammad was the only prophet to make it known that he was not sent only for a certain people, but rather for all the various peoples of the world. The Jews, for example, consider themselves to be a chosen race and that their message is meant exclusively for themselves. Thus, many orthodox Jews do not believe in proselytizing their faith. The New Testament also makes it clear that Jesus’ mission was to the Tribes of Israel. Matthew 10: 5-6 read:
“These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not: But go rather to the lost sheep of the house of Israel.”
Jesus is reported to have said when the Canaanite woman came to him for help,
“I am not sent but unto the lost sheep of the house of Israel” (Matthew 15:24).
This limited mission of Jesus’ is also affirmed in the Quran (61:6). In the case of the Prophet Muhammad, however, God says:
“Say (O Muhammad to the people), ‘O mankind! Verily, I am sent to you all as the Messenger of God…’” (Quran 7:158)
Another verse reads:
“And We have not sent you (O Muhammad) except as a giver of glad tidings and a warner to all mankind.” (Quran 34:28)
There are yet other verses giving the same purport. Prophet Muhammad also stated that he was distinguished from the earlier prophets by five matters. The last he mentioned was:
“[Before] a prophet would be sent to his own people only, while I have been sent to all of mankind.” (Saheeh Al-Bukhari, Saheeh Muslim)
Fourth, the laws and teachings of this message had to be fixed in matters that need to be fixed for all of humankind until the Day of Judgment and guiding yet flexible or accommodating in those matters that need to be open to change due to the changing circumstances of humankind. This shall be discussed in more detail below.
On all of these points, one sees that it is the message of the Prophet Muhammad that fits all of these criteria. Furthermore, all of these aspects make it quite clear that the Prophet Muhammad is qualified and sufficient to be the messenger for all of humankind and that the religion that all humankind should accept is Islam.
 In the same context, Jesus in quoted in Matthew 15:26 as saying about helping the Canaanite woman, “It is not meet to take the children's bread, and cast it to dogs.” Again, God alone knows what parts of the Gospels attributed to Jesus were actually said by him.