Traditional Islam regards Islam as a religion that is different than and distinct from previous revelations. The Qur’an, however, names Itself as a Book confirming the previous ones and completing the religion, namely Islam. Islam, literally, submission to God, is the only religion that has been communicated to all prophets from Adam (pbuh) to Muhammad (pbuh):
“The religion in the sight of God is Islam.“ (Al-e Imran 3:19)
“Say (to them): ‘We have trusted in God. We have trusted in what has been sent down to us and what was sent down to Abraham, Ishmael, Isaac, Jacob and his descendants. We have believed in what was granted to Moses and Jesus, and whatever was granted to prophets by their Master. We make no distinction between any of them. We have submitted ourselves to God. (Nahnu lahu Muslimun)’” (al-Baqarah 2:136)
“Do you say that Abraham, Ishmael, Isaac, Jacob, and their descendants were Jews or Christians? Say (to them): “Do you know better, or does God?” Who is more wrong-doing than he who conceals a truth which has been shown to him by God? God is never heedless of what you are doing.“ (al-Baqarah 2:140)
“Moses said to his people:’Oh my nation! Rely on God if you have trusted in Him and submitted yourselves to Him. (in kuntum Muslimeen)'” (Jonah 10:84)
THE QUR’AN ATTESTS CONFIRMATION TO PREVIOUS DIVINE BOOKS:
To avoid confusion of names and notions, we first have to make the following explanation:
The English word “Torah” and the Hebrew word “Tora= תּוֹרָה” refer to the first five books of the Old Testament, whereas the Arabic word “Taurat = توراة ” mentioned in the Qur’an, refers to the complete Old Testament, or in its Hebrew name: “Tanakh = תַּנַ”ךְ”. Therefore, the word “Torah” in the following English translations of verses, refers to the Tanakh.
The Arabic word “Injeel = إنجيل” mentioned in the Qur’an refers to “Gospel” in English, or in its Greek name: “Evangelion = εὐαγγέλιον”.
The Qur’an does not deny or disregard the previous Scriptures but attests confirmation to them:
“(O Muhammad!) He has sent down to you the Book including the whole truth and confirming the previous ones. He had also sent down the Torah and the Gospel.” (Al-e Imran 3:3)
“God has legislated for you the religion which He enjoined upon Noah. (Oh, Muhammad!) That which God has sent down to you, and that which He enjoined upon Abraham, Moses, and Jesus is: “Keep up this religion, and therein do not separate or divide”.” (Ash-Shura 42:13)
The following narration from Muhammad (a.s.) summarizes what Islam is and for which purpose Prophet Muhammad was sent:
“Jabir reported Messenger Muhammad (ﷺ) as saying: The similitude of mine and that of the previous Prophets (nabi) is like that of a person who built a house and he completed it and made it perfect but for the space of a brick. People entered therein and they were surprised at it and said: Had there been a brick (it would have been complete in all respects). Allah’s Messenger (ﷺ) said: I am that place where the brick (completing the building) is to be placed, and I have come to finalize the chain of Prophets (Nabi).” (Sahih Muslim, The Book of Virtues, 2287 a)
THE GOSPEL BASES ON THE TORAH (TANAKH), AND JESUS FULFILLS THE TORAH:
God taught Jesus both the Torah and the Gospel, because Jesus was also sent to confirm and fulfill the previous law of God:
“Mary said: “Oh my Master! How come I have a child, while no man has touched me?” God said: “Yes it is true (but). God creates whatever He prefers. When He decreed a matter, He merely says, “Be!”, and it comes into existence. He (God) will teach Him (Jesus) the Book and the Wisdom, the Torah and the Gospel.“ (Al-e Imran 3:47-48)
The same principle is mentioned also in the Gospel of Matthew. Jesus (pbuh) said:
“Think not that I have come to abolish the law and the prophets; I have come not to abolish them but to fulfill them.
For truly, I say to you, till heaven and earth pass away, not an iota, not a dot, will pass from the law until all is accomplished.
Whoever then relaxes one of the least of these commandments and teaches men so, shall be called least in the kingdom of heaven; but he who does them and teaches them shall be called great in the kingdom of heaven” (Matthew 5:17-19)
THE TORAH AND THE GOSPEL REQUIRE THEIR BELIEVERS TO COMPLY WITH THE QUR’AN:
All the prophets, except for the final Prophet Muhammad (pbuh), were prescribed to believe in and support the Prophet which would be sent after themselves. So, the chain of revelation would be completed through the efforts of Apostles and the believers easily:
“When God took a covenant from each of the prophets, He said: “If I grant you Book and Wisdom, and then a messenger/Book confirming what is with you comes to you, then you will surely believe in him/It and support him/It.” He (God) said: “Do you agree and accept this heavy burden? ” They said: “We accepted.” God said: “Bear witness to this! I am also a witness with you!”” (Al-e Imran 3:81)
“As for those who follow that Messenger, the Prophet who can neither read nor write, whom they will find described in the Torah and the Gospel (which are) with them; he will enjoin on them that which is right and forbid them that which is wrong. He will make lawful for them all good things and forbid them only from the foul, and he will relieve them of their burden and the fetters that they used to wear.” (Al-A’raf 7:157)
Those who were granted divine Scriptures before the Qur’an have clear references in their Books to the qualities of the forthcoming Book, the Messenger and his acts. So, they could easily recognize the final Book which confirms the Scriptures at their hands:
“Say, ‘Whether you believe It (the Qur’an) or not, those who were given knowledge before It fall down on their faces when It is recited to them, and say, “Glory to our Master! Our Master’s promise has been fulfilled.” They fall down on their faces, weeping, and It (the Quran) increases their respect.'” (al-Isra 17:107-109)
For example, the Gospel has a section in it which shows that the direction of prayer would be changed from Jerusalem to another direction, which has come true through the revelation of the Qur’an:
““Sir,” the woman said, “I can see that you are a prophet. Our ancestors worshiped on this mountain, but you Jews claim that the place where we must worship is in Jerusalem.” “Woman,” Jesus replied, “believe me, a time is coming when you will worship the Father neither on this mountain nor in Jerusalem.” (John 4:19-21)
THE QUR’AN AS THE FINAL LINK OF THE CHAIN OF ISLAM:
Qur’an is the final divine Book that completes the revelation chain of the religion established by God, the religion that always based on submission to God, namely Islam:
“(Oh you who trust in God!)… Today I have perfected your religion for you, completed My blessing upon you, and consented to Islam (total submission to God) as your religion.” (al-Maedah 5:3)
Further reading about the relations of divine Books with each other can be found on the links below:
 The word “rasul = رسول” mentioned in the verse means both “information that is sent” and “the messenger who delivers the sent information” (Mufradat, art. رسل). The information is of higher worth than the messenger, and therefore the Almighty God has decreed: “Muhammad is only a messenger. Messengers have passed on before him. If he dies or gets killed, will you turn about on your heels?” (Al-e Imran 3:144). The information that the Messenger Muhammad (pbuh) brought is gathered in the Quran, and the “rasul” is the Quran Itself, becoming so after his death. Therefore, depending on the context, the word “rasul” is assigned the meaning “the Book of God” within this work, as well as “the Messenger of God”.