I was asked by some non-Muslims, when Aadam and Eve came in this world which religion did they belong to. well I as a Muslim have no doubts on their not being a Muslim but in future if I do come across questions like that, can you please tell me how do I support my answer. Or rather, what would be the best explanation that I can provide them with?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Islam means submission to Allaah, believing that None has the right to be worshipped but Him, obeying Him and fulfilling His Commandments, and declaring oneself free from Shirk (ascribing partners to Allaah) and from the polytheists. Aadam (Adam) (and his wife Eve (Hawwaa'), and all the Prophets after him were Muslims. All of them submitted themselves to the worship of Allaah Alone, obeying Him and fulfilling His Commandments, and declared themselves free from associating partners with Allaah and free from those who associate partners with Him.

Indeed, the Quran explains that Islam is the religion of all the Prophets and Messengers, may Allaah exalt their mention, and that Allaah does not accept from anybody any religion but Islam. Allaah says (what means): {And whoever seeks a religion other than Islam, it will never be accepted of him, and in the Hereafter he will be one of the losers.} [Quran 3:85] Allaah also says (what means): {Truly, the religion with Allaah is Islam.} [Quran 3:19]

Allaah further says about Ibraaheem (what means): {Ibraaheem was neither a Jew nor a Christian, but he was a true Muslim Haneefah (to worship None but Allaah Alone) and he was not of the polytheists.} [Quran 3:67]

Allaah also Says about the Prophet Yoosuf (Joseph) (what means): {Make me die as a Muslim (the one submitting to Your Will), and join me with the righteous.} [Quran 12:101]

In reference to Moosaa (Moses) Allaah Says (what means): {And Moosaa said: "O my people, if you have believed in Allaah, then put your trust in Him if you are Muslims (those who submit to Allaah's will)."} [Quran 10: 84]

In reference to Prophet Nooh (Noah) Allaah Says (what means): {I have been commanded to be one of the Muslims.} [Quran 10: 72]

Allaah says about Ya'qoob (Jacob) (what means): {Or were you witnesses when death approached Ya'qoob, when he said to his sons, "What will you worship after me?" They said, “We will worship your God and the God of your fathers, Ibraaheem and Ismaa'eel (Ishmael) and Isaac - one God. And we are Muslims [in submission] to Him.} [Quran 2:133]

All these verses clarify that Islam was indeed the religion of all Prophets and Messengers from Aadam to our Prophet Muhammad .

Allaah Knows best.