Praise be to Allah, and may peace and blessings be upon the Messenger of Allah.
It is not correct in this matter to distinguish between the Qur’an and Islam, because the Qur’an is the Book that explains Islam and calls to it. As for the detailed laws, each nation had a law appropriate to its time and circumstances, until Allah sent Muhammad ﷺ and revealed the Qur’an to him. Through it, Allah abrogated the previous laws and made following the Qur’an and the law of Islam obligatory upon all people until the Day of Resurrection.
In the revealed texts, Islam is used in two meanings:
First: General Islam. This means affirming the Oneness of Allah Almighty, obeying Him, and following the Messenger whom Allah sent in each era, according to the law that Allah prescribed for his nation at that time.
This is the meaning of Allah’s statement:
“Indeed, the religion with Allah is Islam.” [Āl ʿImrān 3:19]
And His statement:
“Whoever seeks a religion other than Islam, it will never be accepted from him, and in the Hereafter he will be among the losers.” [Āl ʿImrān 3:85]
As for specific Islam, it means affirming the Oneness of Allah Almighty and following the law of the Qur’an that He revealed to our Prophet Muhammad ﷺ.
After the mission of the Prophet ﷺ, no one’s religion is accepted except by following his law, because Allah sent him to all people and made his message universal until the Day of Resurrection.
Allah says:
“Those who follow the Messenger, the unlettered Prophet, whom they find written in the Torah and the Gospel, who enjoins upon them what is right and forbids them what is wrong, makes lawful for them the good things and prohibits for them the impure things, and relieves them of their burdens and the shackles that were upon them. So those who believe in him, honor him, support him, and follow the light that was sent down with him—it is they who will prosper. Say: ‘O mankind, indeed I am the Messenger of Allah to you all, to Him belongs the kingdom of the heavens and the earth. There is no deity except Him; He gives life and causes death. So believe in Allah and His Messenger, the unlettered Prophet, who believes in Allah and His words, and follow him so that you may be guided.’” [Al-Aʿrāf 7:157–158]
Allah Almighty explained that the detailed laws were not identical among all nations. He says:
“For each of you We have prescribed a law and a methodology.” [Al-Mā’idah 5:48]
Thus, the laws that differ between nations may change according to differences in times and circumstances, while the fundamental principles of religion, such as affirming Allah’s Oneness and worshipping Him, remain established in the messages of the prophets.
For this reason, Shaykh ʿAbd al-Raḥmān al-Saʿdī, may Allah have mercy on him, stated that the laws that differ according to nations are those that change according to times and circumstances. As for the major principles that contain benefit and wisdom in every age, they do not differ; rather, all the revealed laws came with them.
Had Allah willed, He could have made all people follow one law, but He made the laws diverse as a matter of wisdom and trial. Allah says:
“Had Allah willed, He could have made you one nation, but [He did so] to test you in what He has given you.” [Al-Mā’idah 5:48]
It is authentically reported that the Prophet ﷺ said:
“I am the closest of all people to Jesus son of Mary, in this world and the Hereafter. The prophets are paternal brothers; their mothers are different, but their religion is one.”
Narrated by al-Bukhari (3443) and Muslim (2365).
Thus, the religion of the prophets is one in its fundamental basis: worshipping Allah alone and obeying Him. However, the detailed laws and methodologies may differ.
Shaykh al-Islam Ibn Taymiyyah, may Allah have mercy on him, explained that religion is like the father because it is the common foundation, while the law and methodology are like the mother because they differ from one revealed law to another.
Accordingly, the law of Moses, peace be upon him, was obligatory to follow in its time; then the law of Jesus, peace be upon him, came. When Allah sent Muhammad ﷺ and revealed the Qur’an to him, following his law became obligatory upon all people.
As for the question of whether the law of the Qur’an would have been suitable for previous nations before the mission of the Prophet ﷺ, this is not something about which one can make a definitive judgment based on speculation. Allah Almighty did not tell us that previous nations were required to follow the Qur’an before it was revealed. Rather, He prescribed for each nation what was appropriate for it.
Therefore, investigating the hypothetical question of whether the Qur’an could have been a law for previous nations, and whether its detailed rulings would have suited them in their respective eras, does not lead to any religious ruling or meaningful benefit. It is an unnecessary attempt to discuss an unseen matter without evidence.
Allah says:
“Say: I do not ask you for any reward for this, nor am I among those who take on unnecessary burdens.” [Ṣād 38:86]
What is important to understand is that Allah Almighty chose a law for each nation, then concluded the messages with the message of Muhammad ﷺ, made the Qur’an the final Book, and made its law universal for all people.
After the mission of the Prophet Muhammad ﷺ and the revelation of the Qur’an, the universal guidance suitable for people and bringing them together upon the truth became following the Qur’an and the law of Islam.
Allah says concerning His Messenger ﷺ:
“And We have not sent you except as a mercy to the worlds.” [Al-Anbiyāʾ 21:107]
The Prophet ﷺ was therefore not sent only to his own people. Rather, Allah sent him as a mercy to the worlds, made his message the final message, and made his Book an authority over the previous Books.
The Qur’an was not an independent law that people were required to follow before the mission of the Prophet Muhammad ﷺ. Each nation had a law that Allah revealed to it, while all the prophets agreed upon the fundamental principle of monotheism and religion.
After the mission of the Prophet ﷺ, following the Qur’an and the law of Islam became obligatory upon all people because the message of Muhammad ﷺ is universal and is the final of the revealed messages.
And Allah knows best.