The Islamic belief concerning human sin is that the individual bears the responsibility for his own sin; no one else should bear this burden for him, nor should he bear the burden for anyone else.
Allah says (interpretation of the meaning):
“And no bearer of burdens shall bear another’s burden…” [Faatir 35:18].
This refutes the idea of original sin. If the father commits a sin, what fault is that of his children and grandchildren? Why should they bear the burden of a sin that someone else committed? The Christian belief that the descendents should bear the sin of their father is the essence of injustice. How can any sane person say that the sin should be carried down the centuries by all of humanity, or that the children, grandchildren and subsequent descendants should be tainted because of their father’s sin?
Secondly, making mistakes is a part of human nature. Our Prophet (pbuh) said, “Every son of Aadam is bound to commit sins…” (reported by al-Tirmidhi, 2423), but Allaah has not left man unable to do anything about the mistakes that he makes. He gives man the opportunity to repent, and so the hadeeth (words of the Prophet (pbuh)) quoted above concludes: “…and the best of those who commit sins are those who repent.” The mercy of Allaah is clear in the teachings of Islam, as Allaah calls His servants (interpretation of the meaning):
“Say, ‘O My servants who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allaah, verily Allaah forgives all sins. Truly, He is Oft-Forgiving, Most Merciful.” [al-Zumar 39:53]
This is human nature, and this is the solution to the problem of sin. But to make this human nature, which is bound to make mistakes, a barrier between the servant and his Lord which will prevent him from ever earning the pleasure of God, and to say that the only way to reach God is through His sending His (so-called) son down to earth to be humiliated and crucified while his father looks on, so that mankind could be forgiven, is an extremely odd idea. Just describing it sounds so unlikely that there is no longer any need to refute it in detail. Once, when discussing this issue with a Christian, I said, “If you say that God sent down His son to be crucified to atone for the sins of the people alive at his time and afterwards, what about those who had come before and died as sinners before the time of Christ, and had no opportunity to know about him and believe in the Crucifixion so that their sins might be forgiven?” All he could say was: “No doubt our priests have an answer to that!” Even if they do have an answer, it is bound to be concocted. There is no real answer.
If you really examine the Christian teaching on human sin with an open mind, you will see that they say that God sacrificed His only son to atone for the sins of mankind, and that this son was a god. If it was true that he was a god who was beaten, insulted and crucified, and died, then this doctrine contains elements of blasphemy because it accuses God of weakness and helplessness. Is God really incapable of forgiving the sins of all His servants with just one word? If He is Able to do all things (and the Christians do not dispute this fact), then why would He need to sacrifice His son in order to achieve the same thing? (Glorified and exalted be He far above what the wrongdoers say about Him!)
“He is the Originator of the heavens and the earth. How can He have children when He has no wife? He created all things and He is the All-Knower of everything.” [al-An’aam 6:101 – interpretation of the meaning]
An ordinary man would not accept anyone harming his child; he would come to his defence, and would never hand him over to an enemy who would insult him, let alone leave him to face the worst kind of death. If this is the attitude of a mere created being, what then of the Creator?
http://www.islamqa.com/en/ref/2690