"Christianity declares that by disobeying God's order not to eat of the forbidden fruit of knowledge, Adam sinned. The sin of Adam Is inherited by all the children of Adam : all human beings are born sinful. The requirement of God's justice is that a price must be paid for every sin. God cannot and will not allow a single sin to go unpunished. Now the only thing which can wipe out sin is the shedding of blood. As St. Paul puts it, "Without the shedding of blood there is no remission (Hebrews 9:22). But this blood must be perfect, sinless, and incorruptible blood. "As the original sin, being directed against God, was of infinite proportion, it demanded infinite recompense." So, Jesus Christ, the Son of God, who came from Heaven, shed his holy, sinless blood, suffered indescribable agony, and died to pay the Penalty for the sins of men. Because Jesus was infinite God, he alone could pay the infinite price of sins. No one can be saved unless he accepts Jesus Christ as his redeemer. Everyone is doomed to suffer eternally in hell because of his sinful nature, unless he accepts atonement made for his sins by Jesus Christ by his blood. [See Cf. God's Plan for your Salvation, Phoenix Arizona, US]

This dogma is divided into three parts: (i) the Original Sin, (ii) the belief that God's Justice requires that the penalty of blood must be paid for sin, and (iii) the belief that Jesus has paid the price for the sins of men by his death on the cross and that salvation is only for those who believe in his vicarious sacrifice.

The Quran rejects the dogma of original sin. It declares that the forgiveness of sins cannot be obtained by the suffering and sacrifice of any other person, human or divine, but by the grace of Allah (God) and our own sincere and persistent efforts to fight against evil and do good:

"That no burdened person (with sins) shall bear the burden (sins) of another. And that man can have nothing but what he does (good or bad), And that his deeds will be seen," Quran (53:38-40).

"Whoever goes right, then he goes right only for the benefit of his ownself. And whoever goes astray, then he goes astray to his own loss. No one laden with burdens can bear another's burden. And We never punish until We have sent a Messenger (to give warning). " Quran (17:15).

Allah in the Quran promises salvation (which in the religion of the Quran means the achievement of nearness to God and the development of all the goodness in man) to all those who believe in God and do good deeds

"Yes, but whoever submits his face (himself) to Allâh (i.e. follows Allâh's Religion of Islâmic Monotheism) and he is a Muhsin (righteous) then his reward is with his Lord (Allâh), on such shall be no fear, nor shall they grieve." Quran (2:112).

The dogma of the Atonement is unsound, for (1) man is not born in sin, (2) God does not require a price to forgive the sinners, and (3) the ideas of substitutionary or vicarious sacrifice is unjust and cruel. By sinning we do not harm God, but ourselves. The stain of sin on our souls can be removed, not by the suffering or death of any other person, whether the latter be willing or unwilling, but by our own repentance, turning away from evil and doing good. And so, when Adam, after the act of disobedience, repented and submitted himself completely to God, his sin was forgiven. Neither is the sin of Adam inherited by the children of Adam, nor did it require the suffering and death of Jesus Christ to be forgiven.

Islam condemns the dogma of the Original Sin and regards the children as pure and sinless at birth. Sin, it says, is not inherited, but it is something which each one acquires for himself by doing what he should not do and not doing what he should do.

Rationally considered also, it would be the height of injustice to condemn the entire human race for the sin committed thousands of years ago by the first parents. Sin is a willful transgression of the law of God or the law of right and wrong. The responsibility or blame for it must lie only on the person committing it, and not on his children. Man is born with a free will, with the inclination and the capacity both to do evil and also to fight against it and do good. It is only when, as a grown-up man, capable of distinguishing between right and wrong, he makes a wrong use of his freedom and falls a prey to temptation, that sin is born in him. That many men and women have resisted and conquered evil inclinations and lived their lives in harmony with the Will of God is clear from the sacred records of all nations. The Bible itself mentions Enoch Noah, Job, John the Baptist, and many others as being perfect and upright and among those who feared God and eschewed evil." [1]

Source (edited):

[1] Islam and Christianity by Mrs. Ulfat Aziz-us-Samad