Original Sin

For the spirit and the soul of Adam, when they were attached to the human world, passed from the world of freedom into the world of bondage, and His descendants continued in bondage. This attachment of the soul and spirit to the human world, which is sin, was inherited by the descendants of Adam, and is the serpent which is always in the midst of, and at enmity with, the spirits and the descendants of Adam. That enmity continues and endures. For attachment to the world has become the cause of the bondage of spirits, and this bondage is identical with sin, which has been transmitted from Adam to His posterity. It is because of this attachment that men have been deprived of essential spirituality and exalted position.
(‘Abdu’l-Bahá, Some Answered Questions, p. 123)

Observe that if, according to the suppositions of the People of the Book, the meaning were taken in its exoteric sense, it would be absolute injustice and complete predestination. If Adam sinned by going near the forbidden tree, what was the sin of the glorious Abraham, and what was the error of Moses the Interlocutor? What was the crime of Noah the Prophet? What was the transgression of Joseph the Truthful? What was the iniquity of the Prophets of God, and what was the trespass of John the Chaste? Would the justice of God have allowed these enlightened Manifestations, on account of the sin of Adam, to find torment in hell until Christ came and by the sacrifice of Himself saved them from excruciating tortures? Such an idea is beyond every law and rule and cannot be accepted by any intelligent person.
(‘Abdu’l-Bahá, Some Answered Questions, p. 125-126)

There are other questions and evidences to be considered. Abraham was a Manifestation of God and a descendant of Adam; likewise, Ishmael, Isaac, Jeremiah and the whole line of prophets including David, Solomon and Aaron were among His posterity. Were all these holy men condemned to a realm of punishment because of a deed committed by the first father, because of a mistake said to have been made by their mutual and remotest ancestor Adam? The explanation is made that when Christ came and sacrificed Himself, all the line of holy Prophets who preceded Him became free from sin and punishment. Even a child could not justly make such an assertion. These interpretations and statements are due to a misunderstanding of the meanings of the Bible.
(‘Abdu’l-Bahá, The Promulgation of Universal Peace, p. 450)

They say that Adam disobeyed the command of God and partook of the fruit of the forbidden tree, thereby committing a sin which was transmitted as a heritage to His posterity. They teach that because of Adam’s sin all His descendants have, likewise, committed transgression and have become responsible through inheritance; that, consequently, all mankind deserves punishment and must make retribution; and that God sent forth His Son as a sacrifice in order that man might be forgiven and the human race delivered from the consequences of Adam’s transgression.
We wish to consider these statements from the standpoint of reason. Could we conceive of the Divinity, Who is Justice itself, inflicting punishment upon the posterity of Adam for Adam’s own sin and disobedience? Even if we should see a governor, an earthly ruler punishing a son for the wrongdoing of his father, we would look upon that ruler as an unjust man. Granted the father committed a wrong, what was the wrong committed by the son? There is no connection between the two. Adam’s sin was not the sin of His posterity, especially as Adam is a thousand generations back of the man today. If the father of a thousand generations committed a sin, is it just to demand that the present generation should suffer the consequences thereof?
(‘Abdu’l-Bahá, The Promulgation of Universal Peace, p. 450)