This is important
This is an important question because every Muslim thinks that the Koran is the last revelation of God and that it replaces the previous ones.
A simple story will help us to answer:
A father in the UK had a son studying at a university in America. For his half-term holiday, his father wanted to invite him to attend a big family wedding. Conscious of the high cost of the plane ticket, the father had decided to offer to pay.
He then sent him a letter informing him of his intention to buy the ticket and mail it to him as soon as possible. So he should not worry about the ticket, (which he couldn’t afford to offer anyway,) and he had only to wait for the one he would send him.
Then, in a second letter, he repeated his promise: “Be patient! Just wait for my next letter,” wrote the father to the son, “the ticket office isn’t yet open.”
When the third letter arrived, the son opened it, and found the promised note, with the remark: “Above all, do not lose it!” The son, of course. was very happy and excited by the prospect of this journey, but then another letter arrived.
In this fourth letter, he noticed something strange: the signature at the bottom seemed to be his father’s, but the message contradicts everything that was in the previous ones. He is told that his ticket is no longer valid, that he must throw it away and buy a new one with his own money! It doesn’t make sense.
Now what should he do? Ignore the first three letters and follow the instructions of the fourth? Impossible! There is a doubt that the first letters were true. The ticket couldn’t possibly be invalidated. The son can see that the last letter is in conflict with the earlier ones.
The same goes for the disciples of Jesus. The Bible contains the Torah, the Zabour, the writings of all the prophets … and finally the Gospel. These books are like so many letters of God for all men. They teach us that our sins deprive us of the peace of God and that we are incapable of redeeming ourselves through our good works in order to go to heaven. But this “bad news” is followed by a “good news”: God, in his goodness, promised that he would provide for our salvation, that a Savior would come. All the prophets of the Old Testament, Abraham, Noah, Moses, and David, testified of this plan of God; Isaiah even says that this Savior would take upon Him the punishment merited by our sins. The Gospel, the final letter of God, reveals to us how God kept and fulfilled His promise: the Savior came, the way is open for all men of all time, salvation, access to Paradise are Free for the believer. The Old Testament and the New Testaments are therefore the two lips by which God speaks with one voice to us. They both reveal exactly the same message. The Old Testament looks forward to the promised Messiah. The New Testament looks back to His life, death, resurrection and ascension to heaven.
Like the son in our history, is it possible that Christians forget all the promises of the letters sent by God In the Bible we are offered a free salvation by trusting the promised Messiah, Jesus. How can we then follow the instructions of a new letter that recommends that we forget all that, and asks them to pay their admission Paradise when they couldn’t recognized their father’s character and previous kind instructions in this final letter?
If I know right now how to receive forgiveness of my sins and how to have the certainty of going to heaven, why should I seek another path? If Jesus is at the heart of God’s plan to save sinners, I can not accept any new instruction that marginalizes him. The Lord of the Rings trilogy does not need a fourth volume to complete it: the victory was total; Star Wars does not require a seventh episode: the six volumes cover the story in question from its origins to victory over the darkness. Similarly, the Christian does not need a new book or a new prophet since Jesus reveals God in all his fulness: He has conquered evil and the Evil One (Satan). In crying out on the cross, “It is accomplished! “Jesus meant that there was nothing else that needed doing. That is why in the last book of the Bible, the Apocalypse, Jesus warns that there is nothing else to say or do more.