Sins - of the Father

All the existing nations had a divine foundation of truth or reality originally, which was intended to be conducive to the unity and accord of mankind, but the light of that reality gradually became obscured. The darkness of superstitions and imitations came and took its place, binding the world of humanity in the chains and fetters of ignorance. Enmity arose among men, increasing to such an extent that nation strove against nation in hatred and violence. War has been a religious and political human heritage.
(‘Abdu’l-Bahá, The Promulgation of Universal Peace, p. 39)

Although it is recognized that the contemporary men of learning are highly qualified in philosophy, arts and crafts, yet were anyone to observe with a discriminating eye he would readily comprehend that most of this knowledge hath been acquired from the sages of the past, for it is they who have laid the foundation of philosophy, reared its structure and reinforced its pillars. Thus doth thy Lord, the Ancient of Days, inform thee. The sages aforetime acquired their knowledge from the Prophets, inasmuch as the latter were the Exponents of divine philosophy and the Revealers of heavenly mysteries. Men quaffed the crystal, living waters of Their utterance, while others satisfied themselves with the dregs. Everyone receiveth a portion according to his measure. Verily He is the Equitable, the Wise.
(Bahá’u’lláh, Tablets of Bahá’u’lláh, p. 144-145)

Among these teachings was the independent investigation of reality so that the world of humanity may be saved from the darkness of imitation and attain to the truth; may tear off and cast away this ragged and outgrown garment of a thousand years ago and may put on the robe woven in the utmost purity and holiness in the loom of reality.
(Selections from the Writings of ‘Abdu’l-Bahá, p. 298)

But the mass of the Christians believe that, as Adam ate of the forbidden tree, He sinned in that He disobeyed, and that the disastrous consequences of this disobedience have been transmitted as a heritage and have remained among His descendants. Hence Adam became the cause of the death of humanity. This explanation is unreasonable and evidently wrong, for it means that all men, even the Prophets and the Messengers of God, without committing any sin or fault, but simply because they are the posterity of Adam, have become without reason guilty sinners, and until the day of the sacrifice of Christ were held captive in hell in painful torment. This is far from the justice of God.
(‘Abdu’l-Bahá, Some Answered Questions, p. 120)

By refusing to carry over the antagonisms and mistrust between the generations which perplex and bedevil modern society, they will again demonstrate the healing and life-giving nature of their religion.
(The Universal House of Justice, 1966 Jun 10, Youth in Every Land)

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? 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 450 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. 449-450)

Demonstrating and perpetuating the historically unequal power relations between genders, family violence severely impedes the full development and advancement of both men and women; replicating itself in generation after generation, it stunts the growth and development of whole societies.
(Bahá’í International Community, 1994 May 26, Creating Violence-Free Families)

From a Bahá’í point of view, humanity’s worship of idols of its own invention is of importance not because of the historical events associated with these forces, however horrifying, but because of the lesson it taught. Looking back on the twilight world in which such diabolical forces loomed over humanity’s future, one must ask what was the weakness in human nature that rendered it vulnerable to such influences. To have seen in someone like Benito Mussolini the figure of a “Man of Destiny", to have felt obliged to understand the racial theories of Adolf Hitler as anything other than the self-evident products of a diseased mind, to have seriously entertained the reinterpretation of human experience through dogmas that had given birth to the Soviet Union of Josef Stalin—so wilful an abandonment of reason on the part of a considerable segment of the intellectual leadership of society demands an accounting to posterity. If undertaken dispassionately, such an evaluation must, sooner or later, focus attention on a truth that runs like a central strand through the Scriptures of all of humanity’s religions. In the words of Bahá’u’lláh: Upon the reality of man ... He hath focused the radiance of all of His names and attributes, and made it a mirror of His own Self.... These energies ... lie, however, latent within him, even as the flame is hidden within the candle and the rays of light are potentially present in the lamp.... Neither the candle nor the lamp can be lighted through their own unaided efforts, nor can it ever be possible for the mirror to free itself from its dross. The consequence of humanity’s infatuation with the ideologies its own mind had conceived was to produce a terrifying acceleration of the process of disintegration that was dissolving the fabric of social life and cultivating the basest impulses of human nature. The brutalization that the first world war had engendered now became an omnipresent feature of social life throughout much of the planet. “Thus have We gathered together the workers of iniquity", Bahá’u’lláh warned over a century earlier. “We see them rushing on towards their idol.... They hasten forward to Hell Fire, and mistake it for light.
(Commissioned by The Universal House of Justice, Century of Light, p. 65)

If a man does a great injustice to another in his life, then, after his death, his son will be despised for having had such a father and in some cases the injury might be so serious that the effect would reach to the grandson, etc., or a man may, by wrong living, fall into consumption and give that disease to his children unto the third or fourth generation. “Both physically and mentally the sins of the fathers may be visited upon the children.”
(‘Abdu’l-Bahá: Daily Lessons Received at ‘Akká 1979 ed., pp. 45-46)

In reference to your question about ancestors and descendants, we have been directed to say that while there are Tablets from Bahá’u’lláh stating that faith in the Manifestation of God on the part of a believer attracts God’s Mercy to the souls of departed parents the House of Justice knows of no text in Bahá’í Writings to support the statement that a believer’s seven past generations and seven generations to descend from him are blessed when that person becomes a Bahá’í. You may also be familiar with the statement of ‘Abdu’l-Bahá that ‘it is permitted to ask for advancement, forgiveness, mercy, beneficence, and blessings for a man after his death...Therefore children...must implore pardon and forgiveness for their parents‘.”
(Universal House of Justice, Lights of Guidance, p. 227)

It is evident that prejudices arising from adherence to religious forms and imitation of ancestral beliefs have hindered the progress of humanity thousands of years. How many wars and battles have been fought, how much division, discord and hatred have been caused by this form of prejudice!
(‘Abdu’l-Bahá, The Promulgation of Universal Peace, p. 39)

Leave the ways of the people and count that the paths of the negligent ones are the lost and destroyed paths, and say: verily, He never walks in your paths and never does as ye have done. He hath already appeared and manifested His right path and taught all His true way.
(Bahá’í Scriptures, p. 233)

Notwithstanding all these evident and significant traditions, all these unmistakable and undisputed allusions, the people have rejected the immaculate Essence of knowledge and of holy utterance, and have turned unto the exponents of rebellion and error. Despite these recorded traditions and revealed utterances, they speak only that which is prompted by their own selfish desires. And should the Essence of Truth reveal that which is contrary to their inclinations and desires, they will straightway denounce Him as an infidel, and will protest saying: “This is contrary to the sayings of the Imams of the Faith and of the resplendent lights. No such thing hath been provided by our inviolable Law.” Even so in this day such worthless statements have been and are being made by these poor mortals.
(Bahá’u’lláh, The Kitáb-i-Ian, p. 240)

The foundations of the divine religions are one. If we investigate these foundations, we discover much ground for agreement, but if we consider the imitations of forms and ancestral beliefs, we find points of disagreement and division; for these imitations differ, while the sources and foundations are one and the same. That is to say, the fundamentals are conducive to unity, but imitations are the cause of disunion and dismemberment. Whosoever is lacking in love for humanity or manifests hatred and bigotry toward any part of it violates the foundation and source of his own belief and is holding to forms and imitations.
(‘Abdu’l-Bahá, The Promulgation of Universal Peace, p. 40)

The variety of inherited qualities comes from strength and weakness of constitution; that is to say, when the two parents are weak, the children will be weak; if they are strong, the children will be robust. In the same way, purity of blood has a great effect; for the pure germ is like the superior stock which exists in plants and animals. For example, you see that children born from a weak and feeble father and mother will naturally have a feeble constitution and weak nerves; they will be afflicted, and will have neither patience, nor endurance, nor resolution, nor perseverance, and will be hasty; for the children inherit the weakness and debility of their parents.
(‘Abdu’l-Bahá, Bahá’í World Faith, p. 318)

Universal education, freedom of thought, the protection of human rights, recognition of the earth’s vast resources as a trust for the whole of humankind, society’s responsibility for the well-being of its citizenry, the promotion of scientific research, even so practical a principle as an international auxiliary language that will advance integration of the earth’s peoples-for all who respond to Bahá’u’lláh’s revelation, these and similar precepts carry the same compelling authority as do the injunctions of scripture against idolatry, theft and false witness.
(Commissioned by The Universal House of Justice, One Common Faith)

We cannot take the teaching that if a believer remains steadfast till the end of his life he will be the means of spiritual awakening of all his ancestors too literally, especially as it is only reported, and not in an authenticated form. However, we can be assured that the true and faithful believer will be in a much better position to intercede for his ancestors, and aid in their development than if he were not spiritually enlightened.
(Shoghi Effendi, Lights of Guidance, p. 227)