In fact, the essence of all the prophets’ messages is what Islam calls for: worshiping Almighty Allah alone and rejecting false deities. Islam is the religion of all prophets; all of them called for what Islam calls for, and so they declared belief in Islam. The message of Islam resembles the messages of all previous prophets of Almighty Allah. Islam completes what was missing in these messages and rectifies the distortions, additions, and misconceptions that befell them. The message of Islam was revealed to confirm whatever Scripture was before it and to verify it.

Sheikh Yusuf Al-Qaradawi states: The word Islam means a wholehearted submission to the will of Almighty Allah, that is worshiping Him alone and without associating any god with Him Most High. This is the core and essential meaning which Almighty Allah sent with all prophets and messengers. Islam, in this sense, is the religion of all prophets, and any other religion [that does not believe in this principle] is not a heavenly one. This essential meaning of Islam is what Almighty Allah refers to in his words, (And We did not send before you any apostle but We revealed to him that there is no god but Me, therefore, serve Me.) (Al-Anbiyaa’ 21: 25)
Hence, the essence of all the prophets’ messages is what Islam calls for—worshiping Almighty Allah alone and rejecting false deities. That is why Almighty Allah says, (Surely, the (true) religion with Allah is Islam) (Aal `Imran 3: 19). This clearly indicates that Almighty Allah does not accept a religion other than Islam.
In this regard, Almighty Allah says, (And whoever desires a religion other than Islam, it shall not be accepted from him, and in the Hereafter, he shall be one of the losers) (Aal `Imran 3: 85).
holding firmly onto this belief, Prophet Nuh (peace and blessings be upon him) said, as quoted in the Qur’an, (But if ye turn back, (consider): no reward have I asked of you: my reward is only due from Allah, and I have been commanded to be of those who submit to Allah’s will (in Islam)) (Yunus 10: 72).
Mind also what Almighty Allah says about Prophet Ibrahim (peace and blessings be upon him), (When his Lord said to him, Be a Muslim, he said: I submit myself to the Lord of the Worlds. And the same did Ibrahim enjoin on his sons and (so did) Ya`qub. O my sons! surely Allah has chosen for you (this) faith, therefore die not unless you are Muslims) (Al-Baqarah 2: 131-32).
Contemplate also on what Almighty Allah says about Prophet Musa,
(Musa said: O my people, if ye do (really) believe in Allah, then in Him put your trust if ye submit (your will to His)) (Yunus 10: 84).
The disciples, companions of Prophet `Isa, also said to him, according to the Qur’an, (We believe in Allah, and do thou bear witness that we are Muslims) (Aal `Imran 3: 52).
the enchanters in the story of Prophet Musa and the Pharaoh, likewise said, according to the Qur’an, (But thou dost wreak thy vengeance on us simply because we believed in the Signs of our Lord when they reached us. Our Lord, pour out on us patience and constancy, and take our souls unto Thee as Muslims (who bow to Thy will)) (Al-A`raf 7: 126).
Consider also what Prophet Sulaiman wrote to the Queen of Sheba (Bilqis) according to the Qur’an, starting his message to her in the name of Allah, Most Gracious, Most Merciful: (Be ye not arrogant against me, but come to me in submission (to the true religion) [Muslims]) (An-Naml 27: 31)
Based on the above, Islam is the religion of all prophets; all of them called for what Islam calls for and declared belief in Islam. Thus, the message of Islam, which Almighty Allah sent with Prophet Muhammad (peace and blessings be upon him) is the seal of the religions, or, to be more precise, the messages of all previous prophets of Almighty Allah. It completes what was missing in these messages and rectifies the distortions, additions, and the like, that befell them. That is why Prophet Muhammad (peace and blessings be upon him) said, “I have been sent (as a messenger from Almighty Allah) so that I perfect the noble ethics.”
So the message of Islam was revealed to confirm whatever Scripture was before it and to verify it, as Almighty Allah addresses Prophet Muhammad: (And unto thee have We revealed the Scripture with the truth, confirming whatever Scripture was before it, and a watcher over it) (Al-Ma’idah 5: 48).
this, again, proves that Islam is the true religion in which all prophets believed. So, it is strange to hear that Prophet Ibrahim (peace and blessings be upon him) was a Jew or Christian; Allah Almighty says about him, (Ibrahim was not a Jew nor a Christian but he was (an) upright (man), a Muslim, and he was not one of the polytheists) (Aal `Imran 3: 67).
this indicates that the religion of Prophet Ibrahim was a full submission to the will of Almighty Allah, which is the core of Islam. Besides, it was Ibrahim who called Muslims by this name. Hence, he is not to be spoken of as belonging to a certain kind of religion. This is because Almighty Allah has willed to call His true religion Islam. Islam, then, is the name of the true faith with which He Almighty sent all His messengers to guide people to the right path.
neither Almighty Allah nor Muslims have called Islam “Mohammedanism,” as is the case with Christianity, which is called so after Jesus Christ. Islam is a joint religion between all prophets. That is why Almighty Allah says, (The same religion has He established for you as that which He enjoined on Nuh, that which We have sent by inspiration to thee and that which We enjoined on Ibrahim, Musa, and `Isa: Namely, that ye should remain steadfast in Religion, and make no divisions therein) (Ash-Shura 42: 13).
Islam, therefore, is of a comprehensive nature, comprising the totality of the true beliefs, noble ethics, and virtues that all prophets called for. It also forbids the fundamental prohibitions shunned by all prophets. With regard to the laws in which the messages of the various prophets differed, these have to do with the minute details of worldly affairs, as would be appropriate to the time and generation in question. Allah Almighty says in this respect, (To each among you have we prescribed a law and an open way) (Al-Ma’idah 5: 48). Some things that were regarded unlawful in the laws of some heavenly messages may be regarded as lawful in other heavenly messages; an example of this is what is recorded in the Qur’an, where Prophet `Isa is reported as saying, ((I have come to you) to attest the law which was before me. And to make lawful to you part of what was (before) forbidden to you) (Aal `Imran 3: 50).
to sum up, Islam is the true religion that has abrogated the rulings of all previous heavenly messages, maintaining the good teachings taught thereby, rectifying what was corrupted thereof, completing what was missing therein, and giving a comprehensive body of laws (Shari`ah) that is eternal and applies to all ages and places.