Why Muslims Believe that Islam is the truth
Many Christians & Jews don't know that Muslims believe in their prophets and holy books. Muslims believe that the Bible and the Torah were changed by people for their personal benefits. This is why God sent Prophet Muhammad, peace be upon him, not with a new religion, but to correct the people who had gone astray, those who were worshipping idols and being misguided by their forefathers.
Islam is the last message to the world and God wants the miracle of Islam to be witnessed by the people from Prophet Muhammad's, peace be upon him, time till the day of Judgment. The miracle is the Qu'ran, Muslims holy book.
Why is the Qur'an a miracle?
1- The Qu'ran is an untouchable book :
After 1400 years, from the begining of Prophet Muhammad's, peace be upon him, message, the Qu'ran has not changed in any way, even as a matter of one charachter. Prooving this is very easy, since you can compare all the versions of the Qu'ran everywhere in the world and you will find them all the same. God ensured that this book would be saved from any changes attempted by human beings. God said in the Qur'an : " We have, without doubt, sent down the Message; and We will assuredly guard it (from corruption)"
2- The Qu'ran contains many scientific facts
that have been discovered recently using computer systems and microscopes. Many scientists have attended conferences dealing with this subject and have themselves accepted Islam. These same scientists have said that it is not possible that Muhammad, peace be upon him, an illiterate man, who lived 1400 years ago, could have discovered such things on his own. God said in the Qur'an : "Soon will We show them Our Signs in the (furthest) regions (of the earth), and in their own souls, until it becomes manifest to them that this is the Truth. Is it not enough that thy Lord doth witness all things" ( Quran 41:53 )
3- The Qu'ran, which is in Arabic, was revealed to the people of the Arabian Gulf who invented the Arabic language. Through Muhammad, peace be upon him, Allah challenged the people who claimed that a human wrote it to emulate such a book. No one from the time of the Prophet till now could write a book that contained the many scientific facts, miracles and similar effects on people that the Qu'ran did and still does today.
4- The Qu'ran had not one Arabic grammar mistake
, which was recognized by the disbelievers at the time of the Prophet, who were the founders of the Arabic language.
These are a few examples of why Muslims believe in the Qur'an.
Here are some verses from God to Muslims encouraging them to invite the People of the Book ( Jews and Christians to Islam ):
God said :
Say: "O People of the Book! Why reject ye the Signs of Allah, when Allah is Himself witness to all ye do?
God tell Muslims to say :
..'We believe in that which had been revealed to us and revealed to you, and our God and your God is One, and unto Him we surrender