Adam: The Original Sin

One of the 3 fundamental issues that Islam and Christianity disagree about is the original sin of Adam. The Quran describes the event of the creation of Adam, his sin and its outcome in various places in the Quran.

Adam Sins.

Adam's sin, and its outcome is depicted in the following verse of the Quran:
"O Adam dwell with your wife in the Garden and enjoy as you wish but approach not this tree or you run into harm and transgression. Then Satan whispered to them in order to reveal to them their shame that was hidden from them and he said:

'Your Lord only forbade you this tree lest you become angels or such beings as live forever.'

And he swore to them both that he was their sincere adviser. So by deceit he brought them to their fall: when they tasted the tree their shame became manifest to them and they began to sew together the leaves of the Garden over their bodies. And their Lord called unto them:

'Did I not forbid you that tree and tell you that Satan was your avowed enemy?' " (Quran 7:19-22). 

Adam and Eve Repent and God Accepts.

When Adam and Eve realized that they have disobeyed God by eating the fruit they called:
"They said:
'Our Lord we have wronged ourselves souls. If You forgive us not and bestow not upon us Your Mercy, we shall certainly be of the losers' " (Quran 7:23)

And God accepts their plea:

".. Thus did Adam disobey his Lord, so he went Astray. Then his Lord chose him, and turned to him with forgiveness, and gave him guidance." (Quran 20:121-122)

The Outcome.

Adam and Eve were instructed not to eat from a certain tree. Satan deceitfully tricked them into disobeying their Lord and as a result:
"(God) said:

'Get down (from the Garden), one of you an enemy to the other [i.e. Adam, Eve, and Satan]. On earth will be a dwelling-place for you and an enjoyment -- for a short time'. He (God) said:

'Therein you shall live, and therein you shall die, and from it you shall be brought out [i.e. resurrected].' " 
(Quran 7:24-25).

Adam and Eve were ordered to leave the Garden which they where in and descend to earth where they and their children will live and die, and where Satan will also be.

The Sin in the Bible.

The Judeo-Christian conception of the creation of Adam and Eve is narrated in detail in Genesis 2:4-3:24. God prohibited both of them from eating the fruits of the forbidden tree. The serpent seduced Eve to eat from it and Eve, in turn, seduced Adam to eat with her. When God rebuked Adam for what he did, he put all the blame on Eve:
"The woman you put here with me she gave me some fruit from the tree and I ate it." Consequently, God said to Eve:

" I will greatly increase your pains in childbearing; with pain you will give birth to children. Your desire will be for your husband and he will rule over you."

To Adam He said:

"Because you listened to your wife and ate from the tree .... Cursed is the ground because of you; through painful toil you will eat of it all the days of your life..."

In Islam (as depicted by the Quranic verses above) Adam doesn't blame Eve for their fault. Both share the responsibility and both receive blame, equally. Furthermore, God doesn't curse Eve for her mistake by "increasing her pains in childbearing".  This concept was a contributing factor for the unequal treatment of women in early Christianity (for more info follow this link ).  Most importantly, God does not curse Adam for committing a sin and that sin in not inherited by the whole world.

Every Person is Responsible for Their Action.

This is what Islam preaches. This is what people throughout the world preach. We consider fair that no person be held accountable or responsible for someone else's mistake. That if blame is due, then it is due on who deserves it. That if punishment is to be made, it ought to be on the one who wronged. We consider that to be fair.
The Quran states:

"That no burdened person (with sins) shall bear the burden (sins) of another. And that man can have nothing but what he does (of good and bad). And that his deeds will be seen, Then he will be recompensed with a full and the best recompense [fair] " (Quran 53:38-41)

The Quranic message is: whatever it is that you do, you are alone will be held responsible for, not your brother, not your father, not your children. This is only fair, and God is Fair. Adam sinned, we agree. But why do his children have to bear something they took no part in? Why is a sacrifice needed to please a Most Merciful God?  A Muslim will answer there is no need for any of that.