Each Prophet was given revelations from God. Anyone since the begining of humankind who submitted to the will of the One and Only God via the teachings of the prophet of his time, was a Muslim. Prophet Abraham (Ibraheem a.s), Joseph (Yusuf a.s), Moses (Musa a.s), David (Dawood a.s), Solomon (Sulaiman a.s), Jesus (Isa a.s) peace be upon them all, were Muslims. “Muslim” means a person who surrenders & submits to the ONE God based on His terms (not based on our desires). Therefore Muslims were around before the arrival of the LAST Prophet, Muhammad (s.a.w.).
Prophet Muhammad (s.a.w.) was NOT the founder of Islam. Islam means = “Peaceful submission to the One and only Merciful and Just God”. Based on this meaning, hence Islam existed since the first human Adam (a.s.) who submitted peacefully to the ONE God.
The last Prophet and Messenger of God did not write the Qur’an. He was known by the people of his time as one who could not read or write. The Qur’an revealed to Prophet Muhammad s.a.w was the last and final revelation from God.
Anyone who followed previous revelations, has to embrace this current and last revelation in human history. The world has changed. Humans have changed. The rules and laws from the previous revelations were no longer compatible for these new generations of humans. The Qur’an is for the last generation of human race on earth before Judgement day.
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أَمۡ كُنتُمۡ شُہَدَآءَ إِذۡ حَضَرَ يَعۡقُوبَ ٱلۡمَوۡتُ إِذۡ قَالَ لِبَنِيهِ مَا تَعۡبُدُونَ مِنۢ بَعۡدِى قَالُواْ نَعۡبُدُ إِلَـٰهَكَ وَإِلَـٰهَ ءَابَآٮِٕكَ إِبۡرَٲهِـۧمَ وَإِسۡمَـٰعِيلَ وَإِسۡحَـٰقَ إِلَـٰهً۬ا وَٲحِدً۬ا وَنَحۡنُ لَهُ ۥ مُسۡلِمُونَ
Or were you present when death came to Jacob, when he said unto his sons: What will you worship after me? They said: We shall worship your God, the God of your fathers, Abraham and Ishmael and Isaac, One God, and unto Him we have surrendered (Muslimoon). (Surah Al-Baqorah – 2:133)